[llvm] [DAG] SelectionDAG.computeKnownBits - add NSW/NUW flags support to ISD::SHL handling (PR #89877)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,126 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 3
+; RUN: llc < %s -mtriple=i686-unknown-unknown -mattr=+sse2 | FileCheck %s --check-prefixes=X86
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=+avx | FileCheck %s --check-prefixes=X64
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s --check-prefixes=CHECK-SSE
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=+avx2 | FileCheck %s --check-prefixes=CHECK-AVX2
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=+avx512f | FileCheck %s --check-prefixes=CHECK-NO-FASTFMA
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mcpu=skx -fp-contract=fast | FileCheck %s --check-prefixes=CHECK-FMA
+
+define i32 @sext_known_nonzero(i16 %xx) {
+; X86-LABEL: sext_known_nonzero:
+; X86:       # %bb.0:
+; X86-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT:    movl $256, %eax # imm = 0x100
+; X86-NEXT:    shll %cl, %eax
+; X86-NEXT:    movzwl	%ax, %eax
+; X86-NEXT:    rep bsfl %eax, %eax
+; X86-NEXT:    retl
+;
+; X64-LABEL: sext_known_nonzero:
+; X64:       # %bb.0:
+; X64-NEXT:    movl %edi, %ecx
+; X64-NEXT:    movl $256, %eax # imm = 0x100
+; X64-NEXT:    # kill: def $cl killed $cl killed $ecx
+; X64-NEXT:    shll %cl, %eax
+; X64-NEXT:    movzwl	%ax, %eax
+; X64-NEXT:    rep bsfl %eax, %eax
+; X64-NEXT:    retq
+  %x = shl nuw nsw i16 256, %xx
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arsenm wrote:

Tests should stress the individual nuw/nsw flags. Also should have some negative tests where the required flag is missing 

https://github.com/llvm/llvm-project/pull/89877