http://llvm.org/bugs/show_bug.cgi?id=14432
Bug #: 14432
Summary: -indvars generates infinite loop
Product: libraries
Version: 3.2
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 9594
--> http://llvm.org/bugs/attachment.cgi?id=9594
test case, compile with "opt -indvars".
The attached .ll file seems to trigger a bug in -indvars with LLVM 3.1, the 3.2
branch (r168527) and SVN trunk (r168548):
In this loop:
---
forcond38:
%__key8.0 = phi i32 [ %tmp81, %noassert68 ], [ 2, %forcond38.preheader ]
%tmp46 = icmp slt i32 %__key8.0, 10
br i1 %tmp46, label %forbody39, label %unrolledend
forbody39:
%tmp51 = sdiv i32 32767, %__key8.0
%tmp57 = sdiv i32 -32768, %__key8.0
%sext33 = shl i32 %tmp51, 16
%sext = shl i32 %tmp51, 16
%tmp66 = icmp eq i32 %sext33, %sext
br i1 %tmp66, label %noassert68, label %assert67
assert67:
tail call void @llvm.trap()
unreachable
noassert68:
%sext34 = shl i32 %tmp57, 16
%sext21 = shl i32 %tmp57, 16
%tmp76 = icmp eq i32 %sext34, %sext21
%tmp81 = add i32 %__key8.0, 1
br i1 %tmp76, label %forcond38, label %assert77
assert77: ; preds = %noassert68
tail call void @llvm.trap()
unreachable
unrolledend: ; preds = %forcond38
ret i32 0
---
-indvars replaces the loop condition with an unconditional jump:
---
- %tmp46 = icmp slt i32 %__key8.0, 10
- br i1 %tmp46, label %forbody39, label %unrolledend
+ br i1 true, label %forbody39, label %unrolledend
---
It would be great if somebody could have a look at this before the 3.2 release,
because this effectively causes a regression in the LDC test suite compared to
LLVM 3.1.
Sorry for the slightly big test case, but bugpoint crashes and I'm not sure if
I'll be able to have another look at the issue before the end of the first
release testing phase.
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