[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Phabricator via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rC319420: [ARM] disable FPU features when using soft floating 
point. (authored by kwalker).

Changed prior to commit:
  https://reviews.llvm.org/D40256?vs=124579=124905#toc

Repository:
  rC Clang

https://reviews.llvm.org/D40256

Files:
  lib/Driver/ToolChains/Arch/ARM.cpp
  test/Driver/arm-cortex-cpus.c
  test/Driver/arm-dotprod.c
  test/Driver/arm-mfpu.c
  test/Preprocessor/arm-target-features.c

Index: lib/Driver/ToolChains/Arch/ARM.cpp
===
--- lib/Driver/ToolChains/Arch/ARM.cpp
+++ lib/Driver/ToolChains/Arch/ARM.cpp
@@ -391,12 +391,22 @@
   } else if (HDivArg)
 getARMHWDivFeatures(D, HDivArg, Args, HDivArg->getValue(), Features);
 
-  // Setting -msoft-float effectively disables NEON because of the GCC
-  // implementation, although the same isn't true of VFP or VFP3.
+  // Setting -msoft-float/-mfloat-abi=soft effectively disables the FPU (GCC
+  // ignores the -mfpu options in this case).
+  // Note that the ABI can also be set implicitly by the target selected.
   if (ABI == arm::FloatABI::Soft) {
-Features.push_back("-neon");
-// Also need to explicitly disable features which imply NEON.
-Features.push_back("-crypto");
+llvm::ARM::getFPUFeatures(llvm::ARM::FK_NONE, Features);
+
+// Disable hardware FP features which have been enabled.
+// FIXME: Disabling vfp2 and neon should be enough as all the other
+//features are dependant on these 2 features in LLVM. However
+//there is currently no easy way to test this in clang, so for
+//now just be explicit and disable all known dependent features
+//as well.
+for (std::string Feature : {"vfp2", "vfp3", "vfp4", "fp-armv8", "fullfp16",
+"neon", "crypto", "dotprod"})
+  if (std::find(std::begin(Features), std::end(Features), "+" + Feature) != std::end(Features))
+Features.push_back("-" + Feature);
   }
 
   // En/disable crc code generation.
Index: test/Driver/arm-cortex-cpus.c
===
--- test/Driver/arm-cortex-cpus.c
+++ test/Driver/arm-cortex-cpus.c
@@ -284,13 +284,13 @@
 // RUN: %clang -target arm -march=armebv8.2-a -mbig-endian -mthumb -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BE-V82A-THUMB %s
 // CHECK-BE-V82A-THUMB: "-cc1"{{.*}} "-triple" "thumbebv8.2a-{{.*}}" "-target-cpu" "generic"
 
-// RUN: %clang -target armv8a -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
 // CHECK-V82A-FP16: "-cc1"{{.*}} "-triple" "armv8.2{{.*}}" "-target-cpu" "generic" {{.*}}"-target-feature" "+fullfp16"
 
 // Once we have CPUs with optional v8.2-A FP16, we will need a way to turn it
 // on and off. Cortex-A53 is a placeholder for now.
-// RUN: %clang -target armv8a -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
-// RUN: %clang -target armv8a -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
 // CHECK-CORTEX-A53-FP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "+fullfp16"
 // CHECK-CORTEX-A53-NOFP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "-fullfp16"
 
Index: test/Driver/arm-mfpu.c
===
--- test/Driver/arm-mfpu.c
+++ test/Driver/arm-mfpu.c
@@ -2,6 +2,8 @@
 
 // RUN: %clang -target arm-linux-eabi %s -### -o %t.o 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-DEFAULT %s
+// CHECK-DEFAULT-NOT: "-target-feature" "+soft-float"
+// CHECK-DEFAULT: "-target-feature" "+soft-float-abi"
 // CHECK-DEFAULT-NOT: "-target-feature" "+vfp2"
 // CHECK-DEFAULT-NOT: "-target-feature" "+vfp3"
 // CHECK-DEFAULT-NOT: "-target-feature" "+d16"
@@ -19,6 +21,10 @@
 
 // RUN: %clang -target arm-linux-eabi -mfpu=vfp %s -### -o %t.o 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-VFP %s
+// RUN: %clang -target arm-linux-eabi -mfpu=vfp %s -mfloat-abi=soft -### -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-SOFT-ABI-FP %s
+// CHECK-VFP-NOT: "-target-feature" "+soft-float"
+// CHECK-VFP: "-target-feature" "+soft-float-abi"
 // CHECK-VFP: "-target-feature" "+vfp2"
 // CHECK-VFP: "-target-feature" "-vfp3"
 // CHECK-VFP: "-target-feature" "-vfp4"
@@ -29,13 +35,21 @@
 // RUN:   | FileCheck --check-prefix=CHECK-VFP3 %s
 // RUN: %clang -target arm-linux-eabi -mfpu=vfpv3 %s -### -o %t.o 2>&1 \
 // RUN:   | FileCheck 

[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Eli Friedman via Phabricator via cfe-commits]

efriedma accepted this revision.
efriedma added a comment.
This revision is now accepted and ready to land.

LGTM


https://reviews.llvm.org/D40256



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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Keith Walker via Phabricator via cfe-commits]

keith.walker.arm updated this revision to Diff 124579.
keith.walker.arm added a comment.

> What are these disabled "R-UN" lines?

Oops!   They shouldn't have been disabled in the patch.

> Do we really need to check every combination like this? I don't think the 
> underlying logic actually varies.

I have reduced the tests in the part to do a check against each architectural 
variant, and then just one check with the different -msoft-float/-mfpu=none 
options.


https://reviews.llvm.org/D40256

Files:
  lib/Driver/ToolChains/Arch/ARM.cpp
  test/Driver/arm-cortex-cpus.c
  test/Driver/arm-dotprod.c
  test/Driver/arm-mfpu.c
  test/Preprocessor/arm-target-features.c

Index: test/Driver/arm-dotprod.c
===
--- test/Driver/arm-dotprod.c
+++ test/Driver/arm-dotprod.c
@@ -4,8 +4,21 @@
 // RUN: %clang -### -target arm -march=armv8.3a %s 2>&1 | FileCheck %s --check-prefix=CHECK-NONE
 // CHECK-NONE-NOT: "-target-feature" "+dotprod"
 
-// RUN: %clang -### -target arm -march=armv8.2a+dotprod %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -march=armv8.3a+dotprod %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -mcpu=cortex-a75 %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -mcpu=cortex-a55 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -march=armv8.2a+dotprod %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -march=armv8.3a+dotprod %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -mcpu=cortex-a75 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -mcpu=cortex-a55 %s 2>&1 | FileCheck %s
 // CHECK: "+dotprod"
+
+// The following default to -msoft-float
+// RUN: %clang -### -target arm -march=armv8.2a+dotprod %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -march=armv8.3a+dotprod %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -mcpu=cortex-a75 %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -mcpu=cortex-a55 %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// We rely on the backend disabling dotprod as it depends on neon, so check that
+// neon is disabled after the dotprod was enabled.
+// CHECK-NO-DOTPROD-NOT: "+dotprod"
Index: test/Driver/arm-cortex-cpus.c
===
--- test/Driver/arm-cortex-cpus.c
+++ test/Driver/arm-cortex-cpus.c
@@ -284,13 +284,13 @@
 // RUN: %clang -target arm -march=armebv8.2-a -mbig-endian -mthumb -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BE-V82A-THUMB %s
 // CHECK-BE-V82A-THUMB: "-cc1"{{.*}} "-triple" "thumbebv8.2a-{{.*}}" "-target-cpu" "generic"
 
-// RUN: %clang -target armv8a -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
 // CHECK-V82A-FP16: "-cc1"{{.*}} "-triple" "armv8.2{{.*}}" "-target-cpu" "generic" {{.*}}"-target-feature" "+fullfp16"
 
 // Once we have CPUs with optional v8.2-A FP16, we will need a way to turn it
 // on and off. Cortex-A53 is a placeholder for now.
-// RUN: %clang -target armv8a -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
-// RUN: %clang -target armv8a -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
 // CHECK-CORTEX-A53-FP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "+fullfp16"
 // CHECK-CORTEX-A53-NOFP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "-fullfp16"
 
Index: test/Driver/arm-mfpu.c
===
--- test/Driver/arm-mfpu.c
+++ test/Driver/arm-mfpu.c
@@ -2,6 +2,8 @@
 
 // RUN: %clang -target arm-linux-eabi %s -### -o %t.o 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-DEFAULT %s
+// CHECK-DEFAULT-NOT: "-target-feature" "+soft-float"
+// CHECK-DEFAULT: "-target-feature" "+soft-float-abi"
 // CHECK-DEFAULT-NOT: "-target-feature" "+vfp2"
 // CHECK-DEFAULT-NOT: "-target-feature" "+vfp3"
 // CHECK-DEFAULT-NOT: "-target-feature" "+d16"
@@ -19,6 +21,10 @@
 
 // RUN: %clang -target arm-linux-eabi -mfpu=vfp %s -### -o %t.o 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-VFP %s
+// RUN: %clang -target arm-linux-eabi -mfpu=vfp %s -mfloat-abi=soft -### -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-SOFT-ABI-FP %s
+// CHECK-VFP-NOT: "-target-feature" "+soft-float"
+// CHECK-VFP: "-target-feature" "+soft-float-abi"
 // CHECK-VFP: "-target-feature" "+vfp2"
 // 

[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Eli Friedman via Phabricator via cfe-commits]

efriedma added inline comments.



Comment at: test/Driver/arm-mfpu.c:301
+// RUN:   | FileCheck --check-prefix=CHECK-SOFT-ABI-FP %s
+// R-UN: %clang -target armv4-linux-gnueabi -mfloat-abi=soft -mfpu=none %s 
-### -c 2>&1 \
+// R-UN:   | FileCheck --check-prefix=CHECK-SOFT-ABI-FP %s

What are these disabled "R-UN" lines?

Do we really need to check every combination like this?  I don't think the 
underlying logic actually varies.


https://reviews.llvm.org/D40256



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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Keith Walker via Phabricator via cfe-commits]

keith.walker.arm updated this revision to Diff 123936.
keith.walker.arm added a comment.

I have updated the patch with the suggested change to use a list of features to 
disable.

I checked that LLVM does indeed implicitly disable features if they are 
dependent on a feature that is explicitly disabled, so in theory we
could just disable "vfp2" and "neon".However I found that this made the 
tests in clang more difficult to write and understand.

For example if a test wants to check that "dotprod" is not enabled:

- with the explicit disabling the check can be: CHECK-NO-DOTPROD-NOT: 
"--target-feature" "+dotprod"
- with implicit disabling the check needs to be something like: 
CHECK-NO-DOTPROD: "--target-feature" "+dotprod" CHECK-NO-DOTPROD: 
"--target-feature" "-neon"

I think this made the tests harder to understand as there is more implicit 
knowledge required to understand what is going on.

For this reason I have gone for still explicitly disabling the dependent FP 
features, with a FIXME so that this could be improved in the future.


https://reviews.llvm.org/D40256

Files:
  lib/Driver/ToolChains/Arch/ARM.cpp
  test/Driver/arm-cortex-cpus.c
  test/Driver/arm-dotprod.c
  test/Driver/arm-mfpu.c
  test/Preprocessor/arm-target-features.c

Index: test/Driver/arm-dotprod.c
===
--- test/Driver/arm-dotprod.c
+++ test/Driver/arm-dotprod.c
@@ -4,8 +4,21 @@
 // RUN: %clang -### -target arm -march=armv8.3a %s 2>&1 | FileCheck %s --check-prefix=CHECK-NONE
 // CHECK-NONE-NOT: "-target-feature" "+dotprod"
 
-// RUN: %clang -### -target arm -march=armv8.2a+dotprod %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -march=armv8.3a+dotprod %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -mcpu=cortex-a75 %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -mcpu=cortex-a55 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -march=armv8.2a+dotprod %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -march=armv8.3a+dotprod %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -mcpu=cortex-a75 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -mcpu=cortex-a55 %s 2>&1 | FileCheck %s
 // CHECK: "+dotprod"
+
+// The following default to -msoft-float
+// RUN: %clang -### -target arm -march=armv8.2a+dotprod %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -march=armv8.3a+dotprod %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -mcpu=cortex-a75 %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -mcpu=cortex-a55 %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// We rely on the backend disabling dotprod as it depends on neon, so check that
+// neon is disabled after the dotprod was enabled.
+// CHECK-NO-DOTPROD-NOT: "+dotprod"
Index: test/Driver/arm-cortex-cpus.c
===
--- test/Driver/arm-cortex-cpus.c
+++ test/Driver/arm-cortex-cpus.c
@@ -284,13 +284,13 @@
 // RUN: %clang -target arm -march=armebv8.2-a -mbig-endian -mthumb -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BE-V82A-THUMB %s
 // CHECK-BE-V82A-THUMB: "-cc1"{{.*}} "-triple" "thumbebv8.2a-{{.*}}" "-target-cpu" "generic"
 
-// RUN: %clang -target armv8a -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
 // CHECK-V82A-FP16: "-cc1"{{.*}} "-triple" "armv8.2{{.*}}" "-target-cpu" "generic" {{.*}}"-target-feature" "+fullfp16"
 
 // Once we have CPUs with optional v8.2-A FP16, we will need a way to turn it
 // on and off. Cortex-A53 is a placeholder for now.
-// RUN: %clang -target armv8a -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
-// RUN: %clang -target armv8a -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
 // CHECK-CORTEX-A53-FP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "+fullfp16"
 // CHECK-CORTEX-A53-NOFP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "-fullfp16"
 
Index: test/Driver/arm-mfpu.c
===
--- test/Driver/arm-mfpu.c
+++ test/Driver/arm-mfpu.c
@@ -2,6 +2,8 @@
 
 // RUN: %clang -target arm-linux-eabi %s -### -o %t.o 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-DEFAULT %s
+// CHECK-DEFAULT-NOT: "-target-feature" "+soft-float"
+// CHECK-DEFAULT: "-target-feature" 

[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Keith Walker via Phabricator via cfe-commits]

keith.walker.arm added inline comments.



Comment at: lib/Driver/ToolChains/Arch/ARM.cpp:406
+const bool HasVFPv4  = (std::find(ItBegin, ItEnd, "+vfpv4") != ItEnd);
+const bool HasFParmv8  = (std::find(ItBegin, ItEnd, "+fp-armv8") != ItEnd);
+const bool HasFullFP16  = (std::find(ItBegin, ItEnd, "+fullfp16") != 
ItEnd);

efriedma wrote:
> I don't like explicitly enumerating the features like this; it'll mess up if 
> there's ever a new feature which isn't explicitly enumerated here.  Can we 
> just do `Features.push_back("-vfpv2")` and depend on that to implicitly 
> disable all the other vfp features?
I'll check on whether disabling a feature on which other features depend 
automatically disables the other features is something that can be relied upon 
(It would seem sensible that one could  but need to check).

That would certainly mean the code could be simplified, although I would also 
need to check the impact on the what is checked in the testing (only test for 
the base feature being disabled because the dependent features are 
automatically disabled).



Comment at: lib/Driver/ToolChains/Arch/ARM.cpp:419
+Features.push_back("-fullfp16");
+
+const bool HasNeon  = (std::find(ItBegin, ItEnd, "+neon") != ItEnd);

compnerd wrote:
> It would be nice to not have these explicitly listed.  But at the very least, 
> I think that having a list and looping through it would be better:
> 
> for (const auto Feature : {"vfpv2", "vfpv3", "vfpv4", "fp-armv8", 
> "fullfp16"})
>   if (std::find(std::begin(Features), std::end(Features), "+" + Feature) 
> == std::end(Features))
> continue;
>   else
> Features.push_back("-" + Feature);
This certainly looks a better way to do it if we do need to provide a list of 
features rather than relying on disabling a base feature on which the other 
features depend. 


https://reviews.llvm.org/D40256



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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Saleem Abdulrasool via Phabricator via cfe-commits]

compnerd added inline comments.



Comment at: lib/Driver/ToolChains/Arch/ARM.cpp:419
+Features.push_back("-fullfp16");
+
+const bool HasNeon  = (std::find(ItBegin, ItEnd, "+neon") != ItEnd);

It would be nice to not have these explicitly listed.  But at the very least, I 
think that having a list and looping through it would be better:

for (const auto Feature : {"vfpv2", "vfpv3", "vfpv4", "fp-armv8", 
"fullfp16"})
  if (std::find(std::begin(Features), std::end(Features), "+" + Feature) == 
std::end(Features))
continue;
  else
Features.push_back("-" + Feature);



Comment at: lib/Driver/ToolChains/Arch/ARM.cpp:429
+if (HasDotProd)
+Features.push_back("-dotprod");
   }

Similar.


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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Eli Friedman via Phabricator via cfe-commits]

efriedma added a comment.

Oh, I see, for some silly reason there are actually *three* -mfloat-abi 
options: hard, soft, and softfp.  hard means float instructions and a 
hard-float calling convention, soft means no floating-point and a soft-float 
convention, and softfp means float instructions and a soft-float convention.  
This is probably worth clarifying with a comment.




Comment at: lib/Driver/ToolChains/Arch/ARM.cpp:406
+const bool HasVFPv4  = (std::find(ItBegin, ItEnd, "+vfpv4") != ItEnd);
+const bool HasFParmv8  = (std::find(ItBegin, ItEnd, "+fp-armv8") != ItEnd);
+const bool HasFullFP16  = (std::find(ItBegin, ItEnd, "+fullfp16") != 
ItEnd);

I don't like explicitly enumerating the features like this; it'll mess up if 
there's ever a new feature which isn't explicitly enumerated here.  Can we just 
do `Features.push_back("-vfpv2")` and depend on that to implicitly disable all 
the other vfp features?


https://reviews.llvm.org/D40256



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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Alex Bradbury via Phabricator via cfe-commits]

asb added subscribers: llvm-commits, asb.
asb added a comment.

It would have been much cleaner if it worked as @efriedma suggests and 
-mfloat-abi was only concerned with the ABI (as its name would suggest), but 
sadly the -mfloat-abi=soft option seems to be defined in GCC to control more 
than just the ABI.

Adding llvm-commits to the subscriber list.


https://reviews.llvm.org/D40256



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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Renato Golin via Phabricator via cfe-commits]

rengolin added a comment.

Wasn't that the mess about -mfpu=softfp?


https://reviews.llvm.org/D40256



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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Eli Friedman via Phabricator via cfe-commits]

efriedma added a comment.

-mfpu controls what floating-point/vector instructions the compiler generates.  
-mfloat-abi controls whether floating-point arguments to functions are passed 
in floating-point registers.  These are completely independent, and we need to 
support using both of them together to generate NEON code with a soft-float 
ABI.  (Android is built like this.)


https://reviews.llvm.org/D40256



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[PATCH] D40256: [ARM] disable FPU features when using soft floating point.

[Keith Walker via Phabricator via cfe-commits]

keith.walker.arm created this revision.
Herald added subscribers: kristof.beyls, javed.absar, aemerson.

To be compatible with GCC if soft floating point is in effect any FPU
specified is effectively ignored, eg,

  -mfloat-abi=soft -fpu=neon

If any floating point features which require FPU hardware are enabled
they must be disable.

There was some support for doing this for NEON, but it did not handle
VFP, nor did it prevent the backend from emitting the build attribute
Tag_FP_arch describing the generated code as using the floating point
hardware if a FPU was specified (even though soft float does not use
the FPU).

Disabling the hardware floating point features for targets which are
compiling for soft float has meant that some tests which were incorrectly
checking for hardware support also needed to be updated.  In such cases,
where appropriate the tests have been updated to check compiling for
soft float and a non-soft float variant (usually softfp).  This was
usually because the target specified in the test defaulted to soft float.


https://reviews.llvm.org/D40256

Files:
  lib/Driver/ToolChains/Arch/ARM.cpp
  test/Driver/arm-cortex-cpus.c
  test/Driver/arm-dotprod.c
  test/Driver/arm-mfpu.c
  test/Preprocessor/arm-target-features.c

Index: test/Driver/arm-dotprod.c
===
--- test/Driver/arm-dotprod.c
+++ test/Driver/arm-dotprod.c
@@ -4,8 +4,19 @@
 // RUN: %clang -### -target arm -march=armv8.3a %s 2>&1 | FileCheck %s --check-prefix=CHECK-NONE
 // CHECK-NONE-NOT: "-target-feature" "+dotprod"
 
-// RUN: %clang -### -target arm -march=armv8.2a+dotprod %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -march=armv8.3a+dotprod %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -mcpu=cortex-a75 %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target arm -mcpu=cortex-a55 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -march=armv8.2a+dotprod %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -march=armv8.3a+dotprod %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -mcpu=cortex-a75 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target arm-linux-eabi -mcpu=cortex-a55 %s 2>&1 | FileCheck %s
 // CHECK: "+dotprod"
+
+// The following default to -msoft-float
+// RUN: %clang -### -target arm -march=armv8.2a+dotprod %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -march=armv8.3a+dotprod %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -mcpu=cortex-a75 %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// RUN: %clang -### -target arm -mcpu=cortex-a55 %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix=CHECK-NO-DOTPROD
+// CHECK-NO-DOTPROD: "-dotprod"
Index: test/Driver/arm-cortex-cpus.c
===
--- test/Driver/arm-cortex-cpus.c
+++ test/Driver/arm-cortex-cpus.c
@@ -284,13 +284,13 @@
 // RUN: %clang -target arm -march=armebv8.2-a -mbig-endian -mthumb -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BE-V82A-THUMB %s
 // CHECK-BE-V82A-THUMB: "-cc1"{{.*}} "-triple" "thumbebv8.2a-{{.*}}" "-target-cpu" "generic"
 
-// RUN: %clang -target armv8a -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -march=armv8.2-a+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-V82A-FP16 %s
 // CHECK-V82A-FP16: "-cc1"{{.*}} "-triple" "armv8.2{{.*}}" "-target-cpu" "generic" {{.*}}"-target-feature" "+fullfp16"
 
 // Once we have CPUs with optional v8.2-A FP16, we will need a way to turn it
 // on and off. Cortex-A53 is a placeholder for now.
-// RUN: %clang -target armv8a -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
-// RUN: %clang -target armv8a -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+fp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-FP16 %s
+// RUN: %clang -target armv8a-linux-eabi -mcpu=cortex-a53+nofp16 -### -c %s 2>&1 | FileCheck --check-prefix CHECK-CORTEX-A53-NOFP16 %s
 // CHECK-CORTEX-A53-FP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "+fullfp16"
 // CHECK-CORTEX-A53-NOFP16: "-cc1" {{.*}}"-target-cpu" "cortex-a53" {{.*}}"-target-feature" "-fullfp16"
 
Index: test/Driver/arm-mfpu.c
===
--- test/Driver/arm-mfpu.c
+++ test/Driver/arm-mfpu.c
@@ -2,6 +2,8 @@
 
 // RUN: %clang -target arm-linux-eabi %s -### -o %t.o 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-DEFAULT %s
+// CHECK-DEFAULT-NOT: "-target-feature" "+soft-float"
+// CHECK-DEFAULT: "-target-feature" "+soft-float-abi"
 // CHECK-DEFAULT-NOT: "-target-feature" "+vfp2"
 // CHECK-DEFAULT-NOT: "-target-feature" "+vfp3"
 // CHECK-DEFAULT-NOT: