[llvm] [AArch64][PAC] Move emission of LR checks in tail calls to AsmPrinter (PR #110705)

[Daniil Kovalev via llvm-commits]

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@@ -0,0 +1,59 @@
+; RUN: llc -mtriple aarch64-linux-pauthtest -o - %s \
+; RUN:     -aarch64-authenticated-lr-check-method=xpac-hint \
+; RUN:     -stop-before=aarch64-ptrauth \
+; RUN:     | FileCheck --check-prefix=MIR %s
+
+; RUN: llc -mtriple aarch64-linux-pauthtest -o - %s \
+; RUN:     -aarch64-authenticated-lr-check-method=xpac-hint \
+; RUN:     | FileCheck --check-prefix=ASM %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
+
+; Test that expansion of AUTH_TCRETURN does not crash due to unavailability of
+; neither x16 nor x17 as a scratch register.
+define i32 @test_scratch_reg_nobti(ptr %callee, ptr %addr) #0 {
+entry:
+  ; Force spilling of LR
+  tail call void asm sideeffect "", "~{lr}"()
+  ; Clobber x0-x15 and x18-x29
+  tail call void asm sideeffect "", "~{x0},~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x13},~{x14},~{x15}"()
+  tail call void asm sideeffect "", "~{x18},~{x19},~{x20},~{x21},~{x22},~{x23},~{x24},~{x25},~{x26},~{x27},~{x28},~{fp}"()
+  %addr.i = ptrtoint ptr %addr to i64
+  %call = tail call i32 %callee() #1 [ "ptrauth"(i32 0, i64 %addr.i) ]
+  ret i32 %call
+}
+; MIR-LABEL: name: test_scratch_reg_nobti
+; MIR:         AUTH_TCRETURN{{ }}
+;
+; ASM-LABEL: @test_scratch_reg_nobti
+; ASM:         autibsp
+; ASM-NEXT:    eor  x17, x30, x30, lsl #1
+; ASM-NEXT:    tbz  x17, #62, .Lauth_success_0
+; ASM-NEXT:    brk  #0xc471
+; ASM-NEXT:  .Lauth_success_0:
+; ASM-NEXT:    braa x0, x16
----------------
kovdan01 wrote:

Is there a reason for not testing the whole function code? It might be unclear why x0 contains `callee` and x16 contains discriminator. At least, it might be worth adding check lines against `mov x16, x1`, `str x0, [sp, #8]` and `ldr x0, [sp, #8]` if checking all spills and reloads is considered an overkill. Also applies to `@test_scratch_reg_bti`.

https://github.com/llvm/llvm-project/pull/110705