[llvm-branch-commits] AArch64: Relax x16/x17 constraint on AUT in certain cases. (PR #132857)

[Anatoly Trosinenko via llvm-branch-commits]

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@@ -191,16 +201,27 @@ define void @test_tailcall_omit_mov_x16_x16(ptr %objptr) #0 {
 define i32 @test_call_omit_extra_moves(ptr %objptr) #0 {
 ; CHECK-LABEL: test_call_omit_extra_moves:
 ; DARWIN-NEXT:   stp     x29, x30, [sp, #-16]!
-; ELF-NEXT:      str     x30, [sp, #-16]!
-; CHECK-NEXT:    ldr     x16, [x0]
-; CHECK-NEXT:    mov     x17, x0
-; CHECK-NEXT:    movk    x17, #6503, lsl #48
-; CHECK-NEXT:    autda   x16, x17
-; CHECK-NEXT:    ldr     x8, [x16]
-; CHECK-NEXT:    movk    x16, #34646, lsl #48
-; CHECK-NEXT:    blraa   x8, x16
-; CHECK-NEXT:    mov     w0, #42
+; DARWIN-NEXT:   ldr     x16, [x0]
+; DARWIN-NEXT:   mov     x17, x0
+; DARWIN-NEXT:   movk    x17, #6503, lsl #48
+; DARWIN-NEXT:   autda   x16, x17
+; DARWIN-NEXT:   ldr     x8, [x16]
+; DARWIN-NEXT:   movk    x16, #34646, lsl #48
+; DARWIN-NEXT:   blraa   x8, x16
+; DARWIN-NEXT:   mov     w0, #42
 ; DARWIN-NEXT:   ldp     x29, x30, [sp], #16
+; ELF-NEXT:      str     x30, [sp, #-16]!
+; ELF-NEXT:      ldr     x8, [x0]
+; ELF-NEXT:      mov     x9, x0
+; ELF-NEXT:      movk    x9, #6503, lsl #48
+; ELF-NEXT:      autda   x8, x9
+; ELF-NEXT:      ldr     x9, [x8]
+; FIXME: Get rid of the x16/x17 constraint on non-Darwin so we can eliminate
+; this mov.
+; ELF-NEXT:      mov     x17, x8
+; ELF-NEXT:      movk    x17, #34646, lsl #48
+; ELF-NEXT:      blraa   x9, x17
+; ELF-NEXT:      mov     w0, #42
 ; ELF-NEXT:      ldr     x30, [sp], #16
 ; CHECK-NEXT:    ret
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atrosinenko wrote:

Looks like `x0` could be updated in-place, as its value doesn't seem to be used after the blend operation.

https://github.com/llvm/llvm-project/pull/132857