[clang] [llvm] New calling convention preserve_none (PR #76868)

[David Li via cfe-commits]

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@@ -0,0 +1,85 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=corei7     | FileCheck --check-prefixes=ALL %s
+; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=corei7-avx | FileCheck --check-prefixes=ALL,AVX %s
+
+; Don't need to preserve registers before using them.
+define preserve_nonecc double @preserve_nonecc1() nounwind {
+entry:
+;ALL-LABEL:   preserve_nonecc1
+;ALL-NOT:     movaps %xmm1
+;ALL-NOT:     movaps %xmm0
+;AVX-NOT:     vmovups %ymm1
+;AVX-NOT:     vmovups %ymm0
+;ALL-NOT:     movaps {{.*}} %xmm0
+;ALL-NOT:     movaps {{.*}} %xmm1
+;AVX-NOT:     vmovups {{.*}} %ymm0
+;AVX-NOT:     vmovups {{.*}} %ymm1
+  call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{rbp},~{xmm0},~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15}"()
+  ret double 0.
+}
+
+; Save/restore live registers across preserve_none function call.
+declare preserve_nonecc double @bar_double(i64, i64)
+define void @preserve_nonecc2() nounwind {
+entry:
+;ALL-LABEL: preserve_nonecc2
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david-xl wrote:

Those xmm registers will be preserved/restored around the call even without the attribute. Perhaps check the the GSRs ?

https://github.com/llvm/llvm-project/pull/76868