Don't reserve R31 on PPC64 unless the frame pointer is needed

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177379 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/PPCRegisterInfo.cpp b/lib/Target/PowerPC/PPCRegisterInfo.cpp
index e2c7221be3762b574a7116585242228742db1d23..74261a3a5046b6ec561ede07c2ba39e43e2232d4 100644 (file)
--- a/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -117,16 +117,15 @@ BitVector PPCRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   }
   
   // On PPC64, r13 is the thread pointer. Never allocate this register.
-  // Note that this is over conservative, as it also prevents allocation of R31
-  // when the FP is not needed.
   if (Subtarget.isPPC64()) {
     Reserved.set(PPC::R13);
-    Reserved.set(PPC::R31);
 
     Reserved.set(PPC::X0);
     Reserved.set(PPC::X1);
     Reserved.set(PPC::X13);
-    Reserved.set(PPC::X31);
+
+    if (PPCFI->needsFP(MF))
+      Reserved.set(PPC::X31);
 
     // The 64-bit SVR4 ABI reserves r2 for the TOC pointer.
     if (Subtarget.isSVR4ABI()) {

diff --git a/test/CodeGen/PowerPC/r31.ll b/test/CodeGen/PowerPC/r31.ll
new file mode 100644 (file)
index 0000000..7ce12f6
--- /dev/null
+++ b/test/CodeGen/PowerPC/r31.ll
@@ -0,0 +1,15 @@
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=g4 | FileCheck %s
+target datalayout = "E-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f128:64:128-n32"
+
+define i64 @foo(i64 %a) nounwind {
+entry:
+  call void asm sideeffect "", "~{r0},~{r3},~{r4},~{r5},~{r6},~{r7},~{r8},~{r9},~{r10},~{r11},~{r12},~{r14},~{r15},~{r16},~{r17},~{r18},~{r19},~{r20},~{r21},~{r22},~{r23},~{r24},~{r25},~{r26},~{r27},~{r28},~{r29},~{r30}"() nounwind
+  br label %return
+
+; CHECK: @foo
+; CHECK: mr 31, 3
+
+return:                                           ; preds = %entry
+  ret i64 %a
+}
+