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Fix codegen to compute the size of an allocation by multiplying the

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size by the array amount as an i32 value instead of promoting from
i32 to i64 then doing the multiply.  Not doing this broke wrap-around
assumptions that the optimizers (validly) made.  The ultimate real
fix for this is to introduce i64 version of alloca and remove mallocinst.

This fixes PR3829

llvm-svn: 67093
This commit is contained in:
Chris Lattner 2009-03-17 19:36:00 +00:00
parent 43ae27a75e
commit e3c442050d
2 changed files with 27 additions and 8 deletions
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25
lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
View File

@ -2763,6 +2763,13 @@ void SelectionDAGLowering::visitAlloca(AllocaInst &I) {
I.getAlignment());
SDValue AllocSize = getValue(I.getArraySize());
AllocSize = DAG.getNode(ISD::MUL, getCurDebugLoc(), AllocSize.getValueType(),
AllocSize,
DAG.getConstant(TySize, AllocSize.getValueType()));
MVT IntPtr = TLI.getPointerTy();
if (IntPtr.bitsLT(AllocSize.getValueType()))
AllocSize = DAG.getNode(ISD::TRUNCATE, getCurDebugLoc(),
@ -2771,9 +2778,6 @@ void SelectionDAGLowering::visitAlloca(AllocaInst &I) {
AllocSize = DAG.getNode(ISD::ZERO_EXTEND, getCurDebugLoc(),
IntPtr, AllocSize);
AllocSize = DAG.getNode(ISD::MUL, getCurDebugLoc(), IntPtr, AllocSize,
DAG.getIntPtrConstant(TySize));
// Handle alignment. If the requested alignment is less than or equal to
// the stack alignment, ignore it. If the size is greater than or equal to
// the stack alignment, we note this in the DYNAMIC_STACKALLOC node.
@ -5425,6 +5429,16 @@ void SelectionDAGLowering::visitInlineAsm(CallSite CS) {
void SelectionDAGLowering::visitMalloc(MallocInst &I) {
SDValue Src = getValue(I.getOperand(0));
// Scale up by the type size in the original i32 type width. Various
// mid-level optimizers may make assumptions about demanded bits etc from the
// i32-ness of the optimizer: we do not want to promote to i64 and then
// multiply on 64-bit targets.
// FIXME: Malloc inst should go away: PR715.
uint64_t ElementSize = TD->getTypePaddedSize(I.getType()->getElementType());
if (ElementSize != 1)
Src = DAG.getNode(ISD::MUL, getCurDebugLoc(), Src.getValueType(),
Src, DAG.getConstant(ElementSize, Src.getValueType()));
MVT IntPtr = TLI.getPointerTy();
if (IntPtr.bitsLT(Src.getValueType()))
@ -5432,11 +5446,6 @@ void SelectionDAGLowering::visitMalloc(MallocInst &I) {
else if (IntPtr.bitsGT(Src.getValueType()))
Src = DAG.getNode(ISD::ZERO_EXTEND, getCurDebugLoc(), IntPtr, Src);
// Scale the source by the type size.
uint64_t ElementSize = TD->getTypePaddedSize(I.getType()->getElementType());
Src = DAG.getNode(ISD::MUL, getCurDebugLoc(), Src.getValueType(),
Src, DAG.getIntPtrConstant(ElementSize));
TargetLowering::ArgListTy Args;
TargetLowering::ArgListEntry Entry;
Entry.Node = Src;

10
test/CodeGen/X86/x86-64-malloc.ll Normal file
View File

@ -0,0 +1,10 @@
; RUN: llvm-as < %s | llc -march=x86-64 | grep {shll.*3, %edi}
; PR3829
; The generated code should multiply by 3 (sizeof i8*) as an i32,
; not as an i64!
define i8** @test(i32 %sz) {
%sub = add i32 %sz, 536870911 ; <i32> [#uses=1]
%call = malloc i8*, i32 %sub ; <i8**> [#uses=1]
ret i8** %call
}