d9507a3e10
The pr description in #94008 mismatches with the code. > + When VT is smaller than ShiftVT, it is safe to use trunc. > + When VT is larger than ShiftVT, it is safe to use zext iff `is_zero_poison` is true (i.e., `opcode == ISD::CTTZ_ZERO_UNDEF`). See also the counterexample `src_shl_cttz2 -> tgt_shl_cttz2` in the alive2 proofs. Closes #94824.
20 lines
654 B
LLVM
20 lines
654 B
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
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; RUN: llc < %s -mtriple=x86_64-linux-gnu | FileCheck %s
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define i16 @pr94824(i8 %x1) {
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; CHECK-LABEL: pr94824:
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; CHECK: # %bb.0: # %entry
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; CHECK-NEXT: orl $256, %edi # imm = 0x100
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; CHECK-NEXT: rep bsfl %edi, %ecx
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; CHECK-NEXT: movl $1, %eax
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; CHECK-NEXT: # kill: def $cl killed $cl killed $ecx
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; CHECK-NEXT: shll %cl, %eax
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; CHECK-NEXT: # kill: def $ax killed $ax killed $eax
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; CHECK-NEXT: retq
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entry:
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%cttz = call i8 @llvm.cttz.i8(i8 %x1, i1 false)
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%ext = zext i8 %cttz to i16
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%shl = shl i16 1, %ext
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ret i16 %shl
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}
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