Implement builtin_{setjmp/longjmp} on PPC

This implements SJLJ lowering on PPC, making the Clang functions
__builtin_{setjmp/longjmp} functional on PPC platforms. The implementation
strategy is similar to that on X86, with the exception that a branch-and-link
variant is used to get the right jump address. Credit goes to Bill Schmidt for
suggesting the use of the unconditional bcl form (instead of the regular bl
instruction) to limit return-address-cache pollution.

Benchmarking the speed at -O3 of:

static jmp_buf env_sigill;

void foo() {
                __builtin_longjmp(env_sigill,1);
}

main() {
	...

        for (int i = 0; i < c; ++i) {
                if (__builtin_setjmp(env_sigill)) {
                        goto done;
                } else {
                        foo();
                }

done:;
        }

	...
}

vs. the same code using the libc setjmp/longjmp functions on a P7 shows that
this builtin implementation is ~4x faster with Altivec enabled and ~7.25x
faster with Altivec disabled. This comparison is somewhat unfair because the
libc version must also save/restore the VSX registers which we don't yet
support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177666 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/Target/PowerPC/PPCRegisterInfo.cpp b/lib/Target/PowerPC/PPCRegisterInfo.cpp
index f3ac23184f..150e241161 100644
--- a/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -105,6 +105,18 @@ PPCRegisterInfo::getCallPreservedMask(CallingConv::ID CC) const {
   return Subtarget.isPPC64() ? CSR_SVR464_RegMask : CSR_SVR432_RegMask;
 }
 
+const uint32_t*
+PPCRegisterInfo::getNoPreservedMask() const {
+  // The naming here is inverted: The CSR_NoRegs_Altivec has the
+  // Altivec registers masked so that they're not saved and restored around
+  // instructions with this preserved mask.
+
+  if (!Subtarget.hasAltivec())
+    return CSR_NoRegs_Altivec_RegMask;
+
+  return CSR_NoRegs_RegMask;
+}
+
 BitVector PPCRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   BitVector Reserved(getNumRegs());
   const PPCFrameLowering *PPCFI =