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R600: Bug 20982 - Avoid undefined left shift of negative value

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I'm not sure what the hardware actually does, so don't
bother trying to fold it for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218057 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matt Arsenault 2014-09-18 15:52:26 +00:00
parent 262d57d578
commit e08e52528b
2 changed files with 14 additions and 9 deletions
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13
lib/Target/R600/AMDGPUISelLowering.cpp
View File

@ -2048,16 +2048,23 @@ SDValue AMDGPUTargetLowering::PerformDAGCombine(SDNode *N,
return DAG.getZeroExtendInReg(BitsFrom, DL, SmallVT);
}
if (ConstantSDNode *Val = dyn_cast<ConstantSDNode>(N->getOperand(0))) {
if (ConstantSDNode *CVal = dyn_cast<ConstantSDNode>(N->getOperand(0))) {
if (Signed) {
// Avoid undefined left shift of a negative in the constant fold.
// TODO: I'm not sure what the behavior of the hardware is, this should
// probably follow that instead.
int32_t Val = CVal->getSExtValue();
if (Val < 0)
return SDValue();
return constantFoldBFE<int32_t>(DAG,
Val->getSExtValue(),
Val,
OffsetVal,
WidthVal);
}
return constantFoldBFE<uint32_t>(DAG,
Val->getZExtValue(),
CVal->getZExtValue(),
OffsetVal,
WidthVal);
}

10
test/CodeGen/R600/llvm.AMDGPU.bfe.i32.ll
View File

@ -1,9 +1,6 @@
; RUN: llc -march=r600 -mcpu=SI -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=FUNC %s
; RUN: llc -march=r600 -mcpu=redwood -show-mc-encoding -verify-machineinstrs < %s | FileCheck -check-prefix=EG -check-prefix=FUNC %s
; http://llvm.org/bugs/show_bug.cgi?id=20982
; REQUIRES: not_ubsan
declare i32 @llvm.AMDGPU.bfe.i32(i32, i32, i32) nounwind readnone
; FUNC-LABEL: @bfe_i32_arg_arg_arg
@ -373,12 +370,13 @@ define void @bfe_i32_constant_fold_test_15(i32 addrspace(1)* %out) nounwind {
ret void
}
; FIXME: This should fold to something
; FUNC-LABEL: @bfe_i32_constant_fold_test_16
; SI-NOT: BFE
; SI: V_MOV_B32_e32 [[VREG:v[0-9]+]], -1
; SI: S_BFE_I32 [[SREG:s[0-9]+]], -1, 0x70001
; SI: V_MOV_B32_e32 [[VREG:v[0-9]+]], [[SREG]]
; SI: BUFFER_STORE_DWORD [[VREG]],
; SI: S_ENDPGM
; EG-NOT: BFE
define void @bfe_i32_constant_fold_test_16(i32 addrspace(1)* %out) nounwind {
%bfe_i32 = call i32 @llvm.AMDGPU.bfe.i32(i32 4294967295, i32 1, i32 7) nounwind readnone
store i32 %bfe_i32, i32 addrspace(1)* %out, align 4