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[X86] Don't try to scale down if that exceeds the bitwidth.

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Fixes the crash reported in PR33844.

llvm-svn: 308503
This commit is contained in:
Davide Italiano 2017-07-19 18:09:46 +00:00
parent 7c394f75f7
commit 9743ca923d
2 changed files with 42 additions and 1 deletions
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5
lib/Target/X86/X86ISelDAGToDAG.cpp
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@ -1055,7 +1055,10 @@ static bool foldMaskAndShiftToScale(SelectionDAG &DAG, SDValue N,
// Scale the leading zero count down based on the actual size of the value.
// Also scale it down based on the size of the shift.
MaskLZ -= (64 - X.getSimpleValueType().getSizeInBits()) + ShiftAmt;
unsigned ScaleDown = (64 - X.getSimpleValueType().getSizeInBits()) + ShiftAmt;
if (MaskLZ < ScaleDown)
return true;
MaskLZ -= ScaleDown;
// The final check is to ensure that any masked out high bits of X are
// already known to be zero. Otherwise, the mask has a semantic impact

38
test/CodeGen/X86/pr33844.ll Normal file
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@ -0,0 +1,38 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -o - %s | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@global = external global i32
@global.1 = external global i64
define void @patatino() {
; CHECK-LABEL: patatino:
; CHECK: # BB#0: # %bb
; CHECK-NEXT: movl {{.*}}(%rip), %eax
; CHECK-NEXT: movl %eax, %ecx
; CHECK-NEXT: shrl $31, %ecx
; CHECK-NEXT: addl $2147483647, %ecx # imm = 0x7FFFFFFF
; CHECK-NEXT: shrl $31, %ecx
; CHECK-NEXT: andl $62, %ecx
; CHECK-NEXT: andl $-536870912, %eax # imm = 0xE0000000
; CHECK-NEXT: orl %ecx, %eax
; CHECK-NEXT: movl %eax, {{.*}}(%rip)
; CHECK-NEXT: retq
bb:
%tmp = load i32, i32* @global
%tmp1 = lshr i32 %tmp, 31
%tmp2 = add nuw nsw i32 %tmp1, 2147483647
%tmp3 = load i64, i64* @global.1
%tmp4 = shl i64 %tmp3, 23
%tmp5 = add nsw i64 %tmp4, 8388639
%tmp6 = trunc i64 %tmp5 to i32
%tmp7 = lshr i32 %tmp2, %tmp6
%tmp8 = load i32, i32* @global
%tmp9 = and i32 %tmp7, 62
%tmp10 = and i32 %tmp8, -536870912
%tmp11 = or i32 %tmp9, %tmp10
store i32 %tmp11, i32* @global
ret void
}