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InstCombine: Don't shrink allocas when combining with a bitcast. 

When considering folding a bitcast of an alloca into the alloca itself,
make sure we don't shrink the amount of memory being allocated, or
things rapidly go sideways.

rdar://13324424

llvm-svn: 176547
This commit is contained in:
Jim Grosbach 2013-03-06 05:44:53 +00:00
parent 2a844b7ff8
commit 95d2eb95c3
3 changed files with 52 additions and 1 deletions
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6
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -104,6 +104,12 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy);
if (CastElTySize == 0 || AllocElTySize == 0) return 0;
// If the allocation has multiple uses, only promote it if we're not
// shrinking the amount of memory being allocated.
uint64_t AllocElTyStoreSize = TD->getTypeStoreSize(AllocElTy);
uint64_t CastElTyStoreSize = TD->getTypeStoreSize(CastElTy);
if (!AI.hasOneUse() && CastElTyStoreSize < AllocElTyStoreSize) return 0;
// See if we can satisfy the modulus by pulling a scale out of the array
// size argument.
unsigned ArraySizeScale;

2
llvm/test/Transforms/Inline/devirtualize.ll
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@ -1,4 +1,4 @@
; RUN: opt -S -basicaa -inline -scalarrepl -instcombine -simplifycfg -instcombine -gvn -globaldce < %s | FileCheck %s
; RUN: opt -S -Os < %s | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0.0"

45
llvm/test/Transforms/InstCombine/2013-03-05-Combine-BitcastTy-Into-Alloca.ll Normal file
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@ -0,0 +1,45 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.9.0"
%struct._my_struct = type <{ [12 x i8], [4 x i8] }>
@initval = common global %struct._my_struct zeroinitializer, align 1
; InstCombine will try to change the %struct._my_struct alloca into an
; allocation of an i96 because of the bitcast to create %2. That's not valid,
; as the other 32 bits of the structure still feed into the return value
define { i64, i64 } @function(i32 %x, i32 %y, i32 %z) nounwind {
; CHECK: @function
; CHECK-NEXT: entry:
; CHECK-NEXT: %retval = alloca %struct._my_struct, align 8
; CHECK-NOT: bitcast i96* %retval to %struct._my_struct*
entry:
%retval = alloca %struct._my_struct, align 8
%k.sroa.0.0.copyload = load i96* bitcast (%struct._my_struct* @initval to i96*), align 1
%k.sroa.1.12.copyload = load i32* bitcast ([4 x i8]* getelementptr inbounds (%struct._my_struct* @initval, i64 0, i32 1) to i32*), align 1
%0 = zext i32 %x to i96
%bf.value = shl nuw nsw i96 %0, 6
%bf.clear = and i96 %k.sroa.0.0.copyload, -288230376151711744
%1 = zext i32 %y to i96
%bf.value2 = shl nuw nsw i96 %1, 32
%bf.shl3 = and i96 %bf.value2, 288230371856744448
%bf.value.masked = and i96 %bf.value, 4294967232
%2 = zext i32 %z to i96
%bf.value8 = and i96 %2, 63
%bf.clear4 = or i96 %bf.shl3, %bf.value.masked
%bf.set5 = or i96 %bf.clear4, %bf.value8
%bf.set10 = or i96 %bf.set5, %bf.clear
%retval.0.cast7 = bitcast %struct._my_struct* %retval to i96*
store i96 %bf.set10, i96* %retval.0.cast7, align 8
%retval.12.idx8 = getelementptr inbounds %struct._my_struct* %retval, i64 0, i32 1
%retval.12.cast9 = bitcast [4 x i8]* %retval.12.idx8 to i32*
store i32 %k.sroa.1.12.copyload, i32* %retval.12.cast9, align 4
%trunc = trunc i96 %bf.set10 to i64
%.fca.0.insert = insertvalue { i64, i64 } undef, i64 %trunc, 0
%retval.8.idx12 = getelementptr inbounds %struct._my_struct* %retval, i64 0, i32 0, i64 8
%retval.8.cast13 = bitcast i8* %retval.8.idx12 to i64*
%retval.8.load14 = load i64* %retval.8.cast13, align 8
%.fca.1.insert = insertvalue { i64, i64 } %.fca.0.insert, i64 %retval.8.load14, 1
ret { i64, i64 } %.fca.1.insert
}