[llvm] [X86] Fold some (setcc (sub (truncate (srl (add X, C1), C2)), C3), CC) patterns to (setcc (cmp (add (truncate (srl X, C2)), C1'), C3), CC) (PR #126448)

[Phoebe Wang via llvm-commits]

=?utf-8?q?João?= Gouveia <jtalonegouveia at gmail.com>,
=?utf-8?q?João?= Gouveia <jtalonegouveia at gmail.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/126448 at github.com>


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@@ -0,0 +1,123 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=x86_64-unknown | FileCheck %s --check-prefixes=X64
+
+; Test for https://github.com/llvm/llvm-project/issues/123239
+
+define i1 @test_ult_trunc_add(i64 %x) {
+; X64-LABEL: test_ult_trunc_add:
+; X64:       # %bb.0: # %entry
+; X64-NEXT:    shrq $48, %rdi
+; X64-NEXT:    addl $-65522, %edi # imm = 0xFFFF000E
+; X64-NEXT:    cmpl $3, %edi
+; X64-NEXT:    setb %al
+; X64-NEXT:    retq
+entry:
+  %add = add i64 %x, 3940649673949184
+  %shr = lshr i64 %add, 48
+  %conv = trunc i64 %shr to i32
+  %res = icmp ult i32 %conv, 3
+  ret i1 %res
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phoebewang wrote:

I'm wondering if we can make it more general, e.g.:
https://alive2.llvm.org/ce/z/zs6NQc
https://godbolt.org/z/jTT99GrGK

I feel the cmp is not necessary here.

https://github.com/llvm/llvm-project/pull/126448