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[AArch64] Fix fast-isel of cbz of i1, i8, i16

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This fixes a miscompilation in the AArch64 fast-isel which was
triggered when a branch is based on an icmp with condition eq or ne,
and type i1, i8 or i16. The cbz instruction compares the whole 32-bit
register, so values with the bottom 1, 8 or 16 bits clear would cause
the wrong branch to be taken.

llvm-svn: 220553
This commit is contained in:
Oliver Stannard 2014-10-24 09:54:41 +00:00
parent 0dfb7c1ecd
commit 4116b199b2
2 changed files with 15 additions and 6 deletions
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6
lib/Target/AArch64/AArch64FastISel.cpp
View File

@ -2181,6 +2181,12 @@ bool AArch64FastISel::emitCompareAndBranch(const BranchInst *BI) {
SrcReg = fastEmitInst_extractsubreg(MVT::i32, SrcReg, SrcIsKill,
AArch64::sub_32);
if ((BW < 32) && !IsBitTest) {
EVT CmpEVT = TLI.getValueType(Ty, true);
SrcReg =
emitIntExt(CmpEVT.getSimpleVT(), SrcReg, MVT::i32, /*isZExt*/ true);
}
// Emit the combined compare and branch instruction.
SrcReg = constrainOperandRegClass(II, SrcReg, II.getNumDefs());
MachineInstrBuilder MIB =

15
test/CodeGen/AArch64/fast-isel-cbz.ll
View File

@ -1,8 +1,9 @@
; RUN: llc -fast-isel -fast-isel-abort -aarch64-atomic-cfg-tidy=0 -verify-machineinstrs -mtriple=aarch64-apple-darwin < %s | FileCheck %s
define i32 @icmp_eq_i1(i1 signext %a) {
define i32 @icmp_eq_i1(i1 %a) {
; CHECK-LABEL: icmp_eq_i1
; CHECK: cbz w0, {{LBB.+_2}}
; CHECK: and [[REG:w[0-9]+]], w0, #0x1
; CHECK: cbz [[REG]], {{LBB.+_2}}
%1 = icmp eq i1 %a, 0
br i1 %1, label %bb1, label %bb2
bb2:
@ -11,9 +12,10 @@ bb1:
ret i32 0
}
define i32 @icmp_eq_i8(i8 signext %a) {
define i32 @icmp_eq_i8(i8 %a) {
; CHECK-LABEL: icmp_eq_i8
; CHECK: cbz w0, {{LBB.+_2}}
; CHECK: uxtb [[REG:w[0-9]+]], w0
; CHECK: cbz [[REG]], {{LBB.+_2}}
%1 = icmp eq i8 %a, 0
br i1 %1, label %bb1, label %bb2
bb2:
@ -22,9 +24,10 @@ bb1:
ret i32 0
}
define i32 @icmp_eq_i16(i16 signext %a) {
define i32 @icmp_eq_i16(i16 %a) {
; CHECK-LABEL: icmp_eq_i16
; CHECK: cbz w0, {{LBB.+_2}}
; CHECK: uxth [[REG:w[0-9]+]], w0
; CHECK: cbz [[REG]], {{LBB.+_2}}
%1 = icmp eq i16 %a, 0
br i1 %1, label %bb1, label %bb2
bb2: