[llvm] [DAGCombine] Propagate truncate to operands (PR #98666)

[Craig Topper via llvm-commits]

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@@ -11,62 +11,63 @@
 define i8 @t0(i32 %a1_wide_orig, i32 %a2_wide_orig, i32 %inc) nounwind {
 ; I386-NOCMOV-LABEL: t0:
 ; I386-NOCMOV:       # %bb.0:
-; I386-NOCMOV-NEXT:    movl {{[0-9]+}}(%esp), %ecx
-; I386-NOCMOV-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; I386-NOCMOV-NEXT:    addl %ecx, %eax
-; I386-NOCMOV-NEXT:    addl {{[0-9]+}}(%esp), %ecx
+; I386-NOCMOV-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
+; I386-NOCMOV-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
+; I386-NOCMOV-NEXT:    addb %cl, %al
+; I386-NOCMOV-NEXT:    addb {{[0-9]+}}(%esp), %cl
 ; I386-NOCMOV-NEXT:    cmpb %cl, %al
 ; I386-NOCMOV-NEXT:    jg .LBB0_2
 ; I386-NOCMOV-NEXT:  # %bb.1:
 ; I386-NOCMOV-NEXT:    movl %ecx, %eax
 ; I386-NOCMOV-NEXT:  .LBB0_2:
-; I386-NOCMOV-NEXT:    # kill: def $al killed $al killed $eax
 ; I386-NOCMOV-NEXT:    retl
 ;
 ; I386-CMOV-LABEL: t0:
 ; I386-CMOV:       # %bb.0:
-; I386-CMOV-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; I386-CMOV-NEXT:    movl {{[0-9]+}}(%esp), %ecx
-; I386-CMOV-NEXT:    addl %eax, %ecx
-; I386-CMOV-NEXT:    addl {{[0-9]+}}(%esp), %eax
+; I386-CMOV-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
+; I386-CMOV-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
+; I386-CMOV-NEXT:    addb %al, %cl
+; I386-CMOV-NEXT:    addb {{[0-9]+}}(%esp), %al
 ; I386-CMOV-NEXT:    cmpb %al, %cl
+; I386-CMOV-NEXT:    movzbl %cl, %ecx
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topperc wrote:

This looks worse

https://github.com/llvm/llvm-project/pull/98666