[llvm] [PowerPC] Utilize `getReservedRegs` to find asm clobberable registers. (PR #99766)

[Chen Zheng via llvm-commits]

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@@ -1146,11 +1146,11 @@ define i64 @test_ints_stack(i32 %i1, i32 %i2, i32 %i3, i32 %i4, i32 %i5, i32 %i6
   ; 64BIT-NEXT:   renamable $r11 = LWZ 0, %fixed-stack.1, implicit-def $x11 :: (load (s32) from %fixed-stack.1)
   ; 64BIT-NEXT:   renamable $x12 = LWZ8 0, %fixed-stack.4 :: (load (s32) from %fixed-stack.4)
   ; 64BIT-NEXT:   renamable $x0 = LWA 0, %fixed-stack.0 :: (load (s32) from %fixed-stack.0)
-  ; 64BIT-NEXT:   renamable $x31 = LD 0, %fixed-stack.2 :: (load (s64) from %fixed-stack.2)
-  ; 64BIT-NEXT:   renamable $x30 = LWA 0, %fixed-stack.3 :: (load (s32) from %fixed-stack.3)
-  ; 64BIT-NEXT:   renamable $r29 = LWZ 0, %fixed-stack.5, implicit-def $x29 :: (load (s32) from %fixed-stack.5)
-  ; 64BIT-NEXT:   renamable $x28 = LWA 0, %fixed-stack.6 :: (load (s32) from %fixed-stack.6)
-  ; 64BIT-NEXT:   renamable $x27 = LD 0, %fixed-stack.7 :: (load (s64) from %fixed-stack.7, align 16)
+  ; 64BIT-NEXT:   renamable $x2 = LD 0, %fixed-stack.2 :: (load (s64) from %fixed-stack.2)
+  ; 64BIT-NEXT:   renamable $x31 = LWA 0, %fixed-stack.3 :: (load (s32) from %fixed-stack.3)
+  ; 64BIT-NEXT:   renamable $r30 = LWZ 0, %fixed-stack.5, implicit-def $x30 :: (load (s32) from %fixed-stack.5)
+  ; 64BIT-NEXT:   renamable $x29 = LWA 0, %fixed-stack.6 :: (load (s32) from %fixed-stack.6)
+  ; 64BIT-NEXT:   renamable $x28 = LD 0, %fixed-stack.7 :: (load (s64) from %fixed-stack.7, align 16)
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chenzheng1030 wrote:

This seems wrong. Now X2 has the highest priority to allocate. We need to use the r31 as the first one. Thus `NumOfGPRsSaved` in trace back table is correct.

https://github.com/llvm/llvm-project/pull/99766