On 12/05/2012 11:45 PM, Hal Finkel wrote:
----- Original Message -----
From: "Tobias Grosser"<[email protected]>
To: "Hal Finkel"<[email protected]>
Cc: [email protected],
[email protected]
Sent: Wednesday, December 5, 2012 4:37:01 PM
Subject: Re: [cfe-commits] [PATCH] Invariants (and Assume Aligned) - Clang
On 12/05/2012 11:29 PM, Hal Finkel wrote:
----- Original Message -----
From: "Tobias Grosser"<[email protected]>
To:
[email protected]
Cc: [email protected], [email protected]
Sent: Wednesday, December 5, 2012 4:04:54 PM
Subject: Re: [cfe-commits] [PATCH] Invariants (and Assume Aligned)
- Clang
On 12/05/2012 09:39 PM, [email protected] wrote:
Test cases have been enhanced. We now use @llvm.invariant.
Index: test/CodeGen/builtin-assume.c
===================================================================
--- /dev/null
+++ test/CodeGen/builtin-assume.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o
-
%s | FileCheck %s
+
+// CHECK: @test1
+int test1(int *a) {
+// CHECK: call void @llvm.invariant(i1
+ __builtin_assume(a != 0);
+ return a[0];
The second check line looks incomplete? Is this intended?
Yes. I did not want to match the variable name specifying the
condition.
[For some reason, I can't see this comment in the web interface].
I have no account for the web interface, but hoped the emails would
show
up there anyway. Is this not the case?
It seems not.
Would you mind adding the entire test case (with some regexp magic)
or
in case this is too much work can you add an example to the
documentation?
Sure. I'll try harder ;)
Does __builtin_assume() basically take an i1 as an
argument and allows an arbitrary set of instructions that lead to
this
i1. Can I have something, like
__builtin_assume(clamp(0, x, 100)>= 0);
__builtin_assume(clamp(0, x, 100)<= 100);
to pass information about the behavior of the function clamp?
Yes; that's the idea. Currently, the only infrastructure I have is to apply
this information to pointer alignments. In the future, the idea is to integrate
this with ScalarEvolution, etc.
I will be the first user. It is perfect to pass information about the
possible values of parameters.
I can see something like
__builtin_assume(B > 0 && B < 100);
or
__builtin_assume(size == 8 || size == 16 || size == 32);
Very helpful. Thanks a lot for making this available.
Tobi
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