[SystemZ] Implement backchain attribute (recommit with fix).
This introduces a SystemZ-specific "backchain" attribute on function, which
enables writing the frame backchain link as specified by the ABI. This will
be used to implement -mbackchain option in clang.
Differential Revision: http://reviews.llvm.org/D19889
Fixed in this version: added RegState::Define and RegState::Kill on R1D
in prologue.
llvm-svn: 268581
diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
index 0bdfaf6..a1f036d 100644
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -354,6 +354,15 @@
uint64_t StackSize = getAllocatedStackSize(MF);
if (StackSize) {
+ // Determine if we want to store a backchain.
+ bool StoreBackchain = MF.getFunction()->hasFnAttribute("backchain");
+
+ // If we need backchain, save current stack pointer. R1 is free at this
+ // point.
+ if (StoreBackchain)
+ BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::LGR))
+ .addReg(SystemZ::R1D, RegState::Define).addReg(SystemZ::R15D);
+
// Allocate StackSize bytes.
int64_t Delta = -int64_t(StackSize);
emitIncrement(MBB, MBBI, DL, SystemZ::R15D, Delta, ZII);
@@ -364,6 +373,10 @@
BuildMI(MBB, MBBI, DL, ZII->get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
SPOffsetFromCFA += Delta;
+
+ if (StoreBackchain)
+ BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::STG))
+ .addReg(SystemZ::R1D, RegState::Kill).addReg(SystemZ::R15D).addImm(0).addReg(0);
}
if (HasFP) {