[llvm] [DAGCombiner] Freeze maybe poison operands when folding select to logic (PR #84924)

[Björn Pettersson via llvm-commits]

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@@ -295,22 +295,28 @@ define float @select_icmp_sle(i32 %x, i32 %y, float %a, float %b) {
 ; Test peephole optimizations for select.
 define zeroext i1 @select_opt1(i1 zeroext %c, i1 zeroext %a) {
 ; CHECK-LABEL: select_opt1
-; CHECK:       orr {{w[0-9]+}}, w0, w1
+; SISEL:       orr [[REG:w[0-9]+]], w0, w1
+; SISEL:       and w0, [[REG]], #0x1
+; FISEL:       orr {{w[0-9]+}}, w0, w1
   %1 = select i1 %c, i1 true, i1 %a
   ret i1 %1
 }
 
 define zeroext i1 @select_opt2(i1 zeroext %c, i1 zeroext %a) {
 ; CHECK-LABEL: select_opt2
-; CHECK:       eor [[REG:w[0-9]+]], w0, #0x1
-; CHECK:       orr {{w[0-9]+}}, [[REG]], w1
+; SISEL:       orn [[REG:w[0-9]+]], w1, w0
+; SISEL:       and w0, [[REG]], #0x1
+; FISEL:       eor [[REG:w[0-9]+]], w0, #0x1
+; FISEL:       orr {{w[0-9]+}}, [[REG]], w1
   %1 = select i1 %c, i1 %a, i1 true
   ret i1 %1
 }
 
 define zeroext i1 @select_opt3(i1 zeroext %c, i1 zeroext %a) {
 ; CHECK-LABEL: select_opt3
-; CHECK:       bic {{w[0-9]+}}, w1, w0
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bjope wrote:

Adding noundef to the arguments doesn't help here. There will still be an AssertZext being added when lowering the arguments.
Not quite sure how we should deal with the (freeze(AssertZext)).

https://github.com/llvm/llvm-project/pull/84924