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Special-case static allocas in IndVarSimplify's loop invariant 

sinking code, since they are special. If the loop preheader happens
to be the entry block of a function, don't sink static allocas
out of it. This fixes PR4775.

llvm-svn: 80010
This commit is contained in:
Dan Gohman 2009-08-25 17:42:10 +00:00
parent 4e9ac2a34b
commit 337d56110e
2 changed files with 36 additions and 0 deletions
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5
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -553,6 +553,11 @@ void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
// dominates the exit block.
if (I->mayHaveSideEffects() || I->mayReadFromMemory())
continue;
// Don't sink static AllocaInsts out of the entry block, which would
// turn them into dynamic allocas!
if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
if (AI->isStaticAlloca())
continue;
// Determine if there is a use in or before the loop (direct or
// otherwise).
bool UsedInLoop = false;

31
llvm/test/Transforms/IndVarSimplify/sink-alloca.ll Normal file
View File

@ -0,0 +1,31 @@
; RUN: llvm-as < %s | opt -indvars | llvm-dis | FileCheck %s
; PR4775
; Indvars shouldn't sink the alloca out of the entry block, even though
; it's not used until after the loop.
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin10.0"
@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 ()* @main to i8*)],
section "llvm.metadata" ; <[1 x i8*]*> [#uses=0]
define i32 @main() nounwind {
; CHECK: entry:
; CHECK-NEXT: %result.i = alloca i32, align 4
entry:
%result.i = alloca i32, align 4 ; <i32*> [#uses=2]
br label %while.cond
while.cond: ; preds = %while.cond, %entry
%call = call i32 @bar() nounwind ; <i32> [#uses=1]
%tobool = icmp eq i32 %call, 0 ; <i1> [#uses=1]
br i1 %tobool, label %while.end, label %while.cond
while.end: ; preds = %while.cond
volatile store i32 0, i32* %result.i
%tmp.i = volatile load i32* %result.i ; <i32> [#uses=0]
ret i32 0
}
declare i32 @bar()