implement Transforms/LoopStrengthReduce/dont-hoist-simple-loop-constants.ll.

We used to emit this code for it:

_test:
        li r2, 1     ;; Value tying up a register for the whole loop
        li r5, 0
LBB_test_1:     ; no_exit.2
        or r6, r5, r5
        li r5, 0
        stw r5, 0(r3)
        addi r5, r6, 1
        addi r3, r3, 4
        add r7, r2, r5  ;; should be addi r7, r5, 1
        cmpwi cr0, r7, 701
        blt cr0, LBB_test_1     ; no_exit.2
LBB_test_2:     ; loopexit.2.loopexit
        addi r2, r6, 2
        stw r2, 0(r4)
        blr

now we emit this:

_test:
        li r2, 0
LBB_test_1:     ; no_exit.2
        or r5, r2, r2
        li r2, 0
        stw r2, 0(r3)
        addi r3, r3, 4
        addi r2, r5, 1
        addi r6, r5, 2   ;; whoa, fold those adds!
        cmpwi cr0, r6, 701
        blt cr0, LBB_test_1     ; no_exit.2
LBB_test_2:     ; loopexit.2.loopexit
        addi r2, r5, 2
        stw r2, 0(r4)
        blr

more improvement coming.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23306 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 245a0266c197a9992a000d99e483f961f67b9c7c..f8b208e47517960a8360d6493dffc37a8ced05cd 100644 (file)
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -826,7 +826,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
     // this by forcing a noop cast to be inserted into the preheader in this
     // case.
     if (Constant *C = dyn_cast<Constant>(BaseV))
-      if (!C->isNullValue()) {
+      if (!C->isNullValue() && !isTargetConstant(Base)) {
         // We want this constant emitted into the preheader!
         BaseV = new CastInst(BaseV, BaseV->getType(), "preheaderinsert",
                              PreInsertPt);