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.

llvm-svn: 177666

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCCallingConv.td b/llvm/lib/Target/PowerPC/PPCCallingConv.td
index caeb1796f7a..2a680661d36 100644
--- a/llvm/lib/Target/PowerPC/PPCCallingConv.td
+++ b/llvm/lib/Target/PowerPC/PPCCallingConv.td
@@ -136,3 +136,8 @@ def CSR_SVR464   : CalleeSavedRegs<(add X14, X15, X16, X17, X18, X19, X20, VRSAV
                                         F27, F28, F29, F30, F31, CR2, CR3, CR4,
                                         V20, V21, V22, V23, V24, V25, V26, V27,
                                         V28, V29, V30, V31)>;
+
+def CSR_NoRegs : CalleeSavedRegs<(add)>;
+
+def CSR_NoRegs_Altivec : CalleeSavedRegs<(add (sequence "V%u", 0, 31), VRSAVE)>;
+