[llvm] [GlobalIsel] Combine G_ADD and G_SUB with constants (PR #97771)

[Thorsten Schütt via llvm-commits]

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@@ -0,0 +1,71 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=aarch64 -verify-machineinstrs %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-SD
+; RUN: llc -mtriple=aarch64 -global-isel -global-isel-abort=2 -verify-machineinstrs %s -o - 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK-GI
+
+
+
+define i64 @APlusC1MinusC2(i64 %a) {
+; CHECK-LABEL: APlusC1MinusC2:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    sub x0, x0, #1
+; CHECK-NEXT:    ret
+entry:
+; fold (A+C1)-C2 -> A+(C1-C2)
+  %add1 = add i64 %a, 5
+  %sub1 = sub i64 %add1, 6
+  ret i64 %sub1
+}
+
+define i64 @C2MinusAPlusC1(i64 %a) {
+; CHECK-LABEL: C2MinusAPlusC1:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    mov w8, #3 // =0x3
+; CHECK-NEXT:    sub x0, x8, x0
+; CHECK-NEXT:    ret
+entry:
+;  fold C2-(A+C1) -> (C2-C1)-A
+  %add1 = add i64 %a, 6
+  %sub1 = sub i64 9, %add1
+  ret i64 %sub1
+}
+
+define i64 @AMinusC1MinusC2(i64 %a) {
+; CHECK-LABEL: AMinusC1MinusC2:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    sub x0, x0, #15
+; CHECK-NEXT:    ret
+entry:
+; fold (A-C1)-C2 -> A-(C1+C2)
+  %sub2 = sub i64 %a, 6
+  %sub1 = sub i64 %sub2, 9
+  ret i64 %sub1
+}
+
+define i64 @C1Minus2MinusC2(i64 %a) {
+; CHECK-LABEL: C1Minus2MinusC2:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    mov w8, #3 // =0x3
+; CHECK-NEXT:    sub x0, x8, x0
+; CHECK-NEXT:    ret
+entry:
+; fold (C1-A)-C2 -> (C1-C2)-A
+  %sub2 = sub i64 14, %a
+  %sub1 = sub i64 %sub2, 11
+  ret i64 %sub1
+}
+
+define i64 @AMinusC2PlusC2(i64 %a) {
+; CHECK-LABEL: AMinusC2PlusC2:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    sub x0, x0, #4
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tschuett wrote:

This `sub` is an `add` in MIR and the comment.

https://github.com/llvm/llvm-project/pull/97771