maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[ARM] Fix computeKnownBits for ARMISD::CMOV 

Summary:
The true and false operands for the CMOV are operands 0 and 1.
ARMISelLowering.cpp::computeKnownBits was looking at operands 1 and 2
instead.  This can cause CMOV instructions to be incorrectly folded into
BFI if value set by the CMOV is another CMOV, whose known bits are
computed incorrectly.

This patch fixes the issue and adds a test case.

Reviewers: kristof.beyls, jmolloy

Subscribers: llvm-commits, aemerson, srhines, rengolin

Differential Revision: https://reviews.llvm.org/D31265

llvm-svn: 298624
This commit is contained in:
Pirama Arumuga Nainar 2017-03-23 16:47:47 +00:00
parent 997a15c3c3
commit bc26482717
2 changed files with 21 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
llvm/lib/Target/ARM/ARMISelLowering.cpp
View File

@ -11695,8 +11695,8 @@ static void computeKnownBits(SelectionDAG &DAG, SDValue Op, APInt &KnownZero,
if (Op.getOpcode() == ARMISD::CMOV) {
APInt KZ2(KnownZero.getBitWidth(), 0);
APInt KO2(KnownOne.getBitWidth(), 0);
computeKnownBits(DAG, Op.getOperand(1), KnownZero, KnownOne);
computeKnownBits(DAG, Op.getOperand(2), KZ2, KO2);
computeKnownBits(DAG, Op.getOperand(0), KnownZero, KnownOne);
computeKnownBits(DAG, Op.getOperand(1), KZ2, KO2);
KnownZero &= KZ2;
KnownOne &= KO2;

19
llvm/test/CodeGen/ARM/no-cmov2bfi.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: llc < %s -mtriple=thumbv7 | FileCheck --check-prefix=CHECK-NOBFI %s
declare zeroext i1 @dummy()
define i8 @test(i8 %a1, i1 %c) {
; CHECK-NOBFI-NOT: bfi
; CHECK-NOBFI: bl dummy
; CHECK-NOBFI: cmp r0, #0
; CHECK-NOBFI: it ne
; CHECK-NOBFI: orrne [[REG:r[0-9]+]], [[REG]], #8
; CHECK-NOBFI: mov r0, [[REG]]
%1 = and i8 %a1, -9
%2 = select i1 %c, i8 %1, i8 %a1
%3 = tail call zeroext i1 @dummy()
%4 = or i8 %2, 8
%ret = select i1 %3, i8 %4, i8 %2
ret i8 %ret
}