Implement an item from the readme, folding vcmp/vcmp. instructions with

identical instructions into a single instruction.  For example, for:

void test(vector float *x, vector float *y, int *P) {
  int v = vec_any_out(*x, *y);
  *x = (vector float)vec_cmpb(*x, *y);
  *P = v;
}

we now generate:

_test:
        mfspr r2, 256
        oris r6, r2, 49152
        mtspr 256, r6
        lvx v0, 0, r4
        lvx v1, 0, r3
        vcmpbfp. v0, v1, v0
        mfcr r4, 2
        stvx v0, 0, r3
        rlwinm r3, r4, 27, 31, 31
        xori r3, r3, 1
        stw r3, 0(r5)
        mtspr 256, r2
        blr

instead of:

_test:
        mfspr r2, 256
        oris r6, r2, 57344
        mtspr 256, r6
        lvx v0, 0, r4
        lvx v1, 0, r3
        vcmpbfp. v2, v1, v0
        mfcr r4, 2
***     vcmpbfp v0, v1, v0
        rlwinm r4, r4, 27, 31, 31
        stvx v0, 0, r3
        xori r3, r4, 1
        stw r3, 0(r5)
        mtspr 256, r2
        blr

Testcase here: CodeGen/PowerPC/vcmp-fold.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27290 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 9 deletions

diff --git a/lib/Target/PowerPC/README_ALTIVEC.txt b/lib/Target/PowerPC/README_ALTIVEC.txt
index 7e013a1..a30b39d 100644
--- a/lib/Target/PowerPC/README_ALTIVEC.txt
+++ b/lib/Target/PowerPC/README_ALTIVEC.txt
@@ -131,15 +131,6 @@ This would fix two problems:
 
 //===----------------------------------------------------------------------===//
 
-Two identical comparisons in predicate and nonpredicate form like this:
-
-a = vec_cmpb(x, y);
-b = vec_any_out(x, y);
-
-Should turn into one "." compare instruction, not a dot and "nondot" form.
-
-//===----------------------------------------------------------------------===//
-
 Instcombine llvm.ppc.altivec.vperm with an immediate into a shuffle operation.
 
 //===----------------------------------------------------------------------===//