[llvm] e2b9318 - [PowerPC] Only make copies of registers on stack in variadic function when va_start is called

[Kai Luo via llvm-commits]

Author: Kai Luo
Date: 2020-07-09T07:18:17Z
New Revision: e2b93185b84bd88264377f785465933a89faa4f8

URL: https://github.com/llvm/llvm-project/commit/e2b93185b84bd88264377f785465933a89faa4f8
DIFF: https://github.com/llvm/llvm-project/commit/e2b93185b84bd88264377f785465933a89faa4f8.diff

LOG: [PowerPC] Only make copies of registers on stack in variadic function when va_start is called

On PPC64, for a variadic function, if va_start is not called, it won't
access any variadic argument on stack, thus we can save stores of
registers used to pass arguments.

Differential Revision: https://reviews.llvm.org/D82361

Added: 
    

Modified: 
    llvm/lib/Target/PowerPC/PPCISelLowering.cpp
    llvm/test/CodeGen/PowerPC/legalize-vaarg.ll
    llvm/test/CodeGen/PowerPC/ppc64-varargs.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index ff8e2382ec65..229c5a76010c 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -4299,7 +4299,11 @@ SDValue PPCTargetLowering::LowerFormalArguments_64SVR4(
 
   // If the function takes variable number of arguments, make a frame index for
   // the start of the first vararg value... for expansion of llvm.va_start.
-  if (isVarArg) {
+  // On ELFv2ABI spec, it writes:
+  // C programs that are intended to be *portable* across 
diff erent compilers
+  // and architectures must use the header file <stdarg.h> to deal with variable
+  // argument lists.
+  if (isVarArg && MFI.hasVAStart()) {
     int Depth = ArgOffset;
 
     FuncInfo->setVarArgsFrameIndex(

diff  --git a/llvm/test/CodeGen/PowerPC/legalize-vaarg.ll b/llvm/test/CodeGen/PowerPC/legalize-vaarg.ll
index 296dea2f1f21..d937acc09c64 100644
--- a/llvm/test/CodeGen/PowerPC/legalize-vaarg.ll
+++ b/llvm/test/CodeGen/PowerPC/legalize-vaarg.ll
@@ -6,13 +6,6 @@ define <8 x i32> @test_large_vec_vaarg(i32 %n, ...) {
 ; BE-LABEL: test_large_vec_vaarg:
 ; BE:       # %bb.0:
 ; BE-NEXT:    ld 3, -8(1)
-; BE-NEXT:    std 4, 56(1)
-; BE-NEXT:    std 5, 64(1)
-; BE-NEXT:    std 6, 72(1)
-; BE-NEXT:    std 7, 80(1)
-; BE-NEXT:    std 8, 88(1)
-; BE-NEXT:    std 9, 96(1)
-; BE-NEXT:    std 10, 104(1)
 ; BE-NEXT:    addi 3, 3, 15
 ; BE-NEXT:    rldicr 3, 3, 0, 59
 ; BE-NEXT:    addi 4, 3, 16
@@ -28,15 +21,8 @@ define <8 x i32> @test_large_vec_vaarg(i32 %n, ...) {
 ; LE-LABEL: test_large_vec_vaarg:
 ; LE:       # %bb.0:
 ; LE-NEXT:    ld 3, -8(1)
-; LE-NEXT:    std 4, 40(1)
-; LE-NEXT:    std 5, 48(1)
-; LE-NEXT:    std 6, 56(1)
-; LE-NEXT:    std 7, 64(1)
 ; LE-NEXT:    addi 3, 3, 15
 ; LE-NEXT:    rldicr 3, 3, 0, 59
-; LE-NEXT:    std 8, 72(1)
-; LE-NEXT:    std 9, 80(1)
-; LE-NEXT:    std 10, 88(1)
 ; LE-NEXT:    addi 4, 3, 31
 ; LE-NEXT:    addi 5, 3, 16
 ; LE-NEXT:    rldicr 4, 4, 0, 59

diff  --git a/llvm/test/CodeGen/PowerPC/ppc64-varargs.ll b/llvm/test/CodeGen/PowerPC/ppc64-varargs.ll
index 56816aee6704..5aeedbf13e0b 100644
--- a/llvm/test/CodeGen/PowerPC/ppc64-varargs.ll
+++ b/llvm/test/CodeGen/PowerPC/ppc64-varargs.ll
@@ -7,29 +7,12 @@
 define i32 @f(...) nounwind {
 ; BE-LABEL: f:
 ; BE:       # %bb.0: # %entry
-; BE-NEXT:    mr r11, r3
 ; BE-NEXT:    li r3, 0
-; BE-NEXT:    std r11, 48(r1)
-; BE-NEXT:    std r4, 56(r1)
-; BE-NEXT:    std r5, 64(r1)
-; BE-NEXT:    std r6, 72(r1)
-; BE-NEXT:    std r7, 80(r1)
-; BE-NEXT:    std r8, 88(r1)
-; BE-NEXT:    std r9, 96(r1)
-; BE-NEXT:    std r10, 104(r1)
 ; BE-NEXT:    blr
 ;
 ; LE-LABEL: f:
 ; LE:       # %bb.0: # %entry
-; LE-NEXT:    std r3, 32(r1)
 ; LE-NEXT:    li r3, 0
-; LE-NEXT:    std r4, 40(r1)
-; LE-NEXT:    std r5, 48(r1)
-; LE-NEXT:    std r6, 56(r1)
-; LE-NEXT:    std r7, 64(r1)
-; LE-NEXT:    std r8, 72(r1)
-; LE-NEXT:    std r9, 80(r1)
-; LE-NEXT:    std r10, 88(r1)
 ; LE-NEXT:    blr
 entry:
   ret i32 0