[llvm] f124e59 - [TypePromotionPass] Don't treat phi's as ToPromote

[David Green via llvm-commits]

Author: David Green
Date: 2022-09-13T08:57:15+01:00
New Revision: f124e59b2e515d65e0b941826467e08de5ba97b0

URL: https://github.com/llvm/llvm-project/commit/f124e59b2e515d65e0b941826467e08de5ba97b0
DIFF: https://github.com/llvm/llvm-project/commit/f124e59b2e515d65e0b941826467e08de5ba97b0.diff

LOG: [TypePromotionPass] Don't treat phi's as ToPromote

This attempts to stop the type promotion pass transforming where it is
not profitable, by not marking PhiNodes as ToPromote and being more
aggressive about pulling extends out of loops.

Differential Revision: https://reviews.llvm.org/D133203

Added: 
    

Modified: 
    llvm/lib/CodeGen/TypePromotion.cpp
    llvm/test/CodeGen/AArch64/typepromotion-cost.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/TypePromotion.cpp b/llvm/lib/CodeGen/TypePromotion.cpp
index 058a18036dcf..6a747a31eabd 100644
--- a/llvm/lib/CodeGen/TypePromotion.cpp
+++ b/llvm/lib/CodeGen/TypePromotion.cpp
@@ -168,7 +168,7 @@ class TypePromotion : public FunctionPass {
   // Is V an instruction thats result can trivially promoted, or has safe
   // wrapping.
   bool isLegalToPromote(Value *V);
-  bool TryToPromote(Value *V, unsigned PromotedWidth);
+  bool TryToPromote(Value *V, unsigned PromotedWidth, const LoopInfo &LI);
 
 public:
   static char ID;
@@ -762,7 +762,8 @@ bool TypePromotion::isLegalToPromote(Value *V) {
   return false;
 }
 
-bool TypePromotion::TryToPromote(Value *V, unsigned PromotedWidth) {
+bool TypePromotion::TryToPromote(Value *V, unsigned PromotedWidth,
+                                 const LoopInfo &LI) {
   Type *OrigTy = V->getType();
   TypeSize = OrigTy->getPrimitiveSizeInBits().getFixedSize();
   SafeToPromote.clear();
@@ -856,6 +857,7 @@ bool TypePromotion::TryToPromote(Value *V, unsigned PromotedWidth) {
 
   unsigned ToPromote = 0;
   unsigned NonFreeArgs = 0;
+  unsigned NonLoopSources = 0, LoopSinks = 0;
   SmallPtrSet<BasicBlock *, 4> Blocks;
   for (auto *CV : CurrentVisited) {
     if (auto *I = dyn_cast<Instruction>(CV))
@@ -865,9 +867,16 @@ bool TypePromotion::TryToPromote(Value *V, unsigned PromotedWidth) {
       if (auto *Arg = dyn_cast<Argument>(CV))
         if (!Arg->hasZExtAttr() && !Arg->hasSExtAttr())
           ++NonFreeArgs;
+      if (!isa<Instruction>(CV) ||
+          !LI.getLoopFor(cast<Instruction>(CV)->getParent()))
+        ++NonLoopSources;
       continue;
     }
 
+    if (isa<PHINode>(CV))
+      continue;
+    if (LI.getLoopFor(cast<Instruction>(CV)->getParent()))
+      ++LoopSinks;
     if (Sinks.count(cast<Instruction>(CV)))
       continue;
     ++ToPromote;
@@ -875,8 +884,8 @@ bool TypePromotion::TryToPromote(Value *V, unsigned PromotedWidth) {
 
   // DAG optimizations should be able to handle these cases better, especially
   // for function arguments.
-  if (!isa<PHINode>(V) && (ToPromote < 2 || (Blocks.size() == 1 &&
-                                             (NonFreeArgs > SafeWrap.size()))))
+  if (!isa<PHINode>(V) && !(LoopSinks && NonLoopSources) &&
+      (ToPromote < 2 || (Blocks.size() == 1 && NonFreeArgs > SafeWrap.size())))
     return false;
 
   IRPromoter Promoter(*Ctx, PromotedWidth, CurrentVisited, Sources, Sinks,
@@ -958,7 +967,7 @@ bool TypePromotion::runOnFunction(Function &F) {
                             << "register for ZExt type\n");
           continue;
         }
-        MadeChange |= TryToPromote(Phi, PromoteWidth);
+        MadeChange |= TryToPromote(Phi, PromoteWidth, LI);
       } else if (auto *ICmp = dyn_cast<ICmpInst>(&I)) {
         // Search up from icmps to try to promote their operands.
         // Skip signed or pointer compares
@@ -970,7 +979,7 @@ bool TypePromotion::runOnFunction(Function &F) {
         for (auto &Op : ICmp->operands()) {
           if (auto *OpI = dyn_cast<Instruction>(Op)) {
             if (auto PromotedWidth = GetPromoteWidth(OpI)) {
-              MadeChange |= TryToPromote(OpI, PromotedWidth);
+              MadeChange |= TryToPromote(OpI, PromotedWidth, LI);
               break;
             }
           }

diff  --git a/llvm/test/CodeGen/AArch64/typepromotion-cost.ll b/llvm/test/CodeGen/AArch64/typepromotion-cost.ll
index f4a8f2ecf58b..c1b3057bfbfd 100644
--- a/llvm/test/CodeGen/AArch64/typepromotion-cost.ll
+++ b/llvm/test/CodeGen/AArch64/typepromotion-cost.ll
@@ -16,7 +16,6 @@ define i32 @needless_promotion(ptr nocapture noundef readonly %S, i64 noundef %r
 ; CHECK-O2-NEXT:  .LBB0_3:
 ; CHECK-O2-NEXT:    mov w9, #1
 ; CHECK-O2-NEXT:  .LBB0_4: // %lor.end.sink.split
-; CHECK-O2-NEXT:    and w8, w8, #0xffff
 ; CHECK-O2-NEXT:    cmp w8, w9
 ; CHECK-O2-NEXT:    cset w0, eq
 ; CHECK-O2-NEXT:    ret
@@ -32,13 +31,11 @@ define i32 @needless_promotion(ptr nocapture noundef readonly %S, i64 noundef %r
 ; CHECK-O3-NEXT:    cbz x1, .LBB0_4
 ; CHECK-O3-NEXT:  // %bb.2:
 ; CHECK-O3-NEXT:    mov w9, #2
-; CHECK-O3-NEXT:    and w8, w8, #0xffff
 ; CHECK-O3-NEXT:    cmp w8, w9
 ; CHECK-O3-NEXT:    cset w0, eq
 ; CHECK-O3-NEXT:    ret
 ; CHECK-O3-NEXT:  .LBB0_3:
 ; CHECK-O3-NEXT:    mov w9, #1
-; CHECK-O3-NEXT:    and w8, w8, #0xffff
 ; CHECK-O3-NEXT:    cmp w8, w9
 ; CHECK-O3-NEXT:    cset w0, eq
 ; CHECK-O3-NEXT:    ret
@@ -69,10 +66,11 @@ lor.end:                                          ; preds = %lor.end.sink.split,
 define i8 @loopcmp(ptr nocapture noundef readonly %x, i8 noundef %y) {
 ; CHECK-O2-LABEL: loopcmp:
 ; CHECK-O2:       // %bb.0: // %entry
+; CHECK-O2-NEXT:    and w9, w1, #0xff
 ; CHECK-O2-NEXT:  .LBB1_1: // %while.cond
 ; CHECK-O2-NEXT:    // =>This Inner Loop Header: Depth=1
 ; CHECK-O2-NEXT:    ldrb w8, [x0], #1
-; CHECK-O2-NEXT:    cmp w8, w1, uxtb
+; CHECK-O2-NEXT:    cmp w8, w9
 ; CHECK-O2-NEXT:    b.lo .LBB1_1
 ; CHECK-O2-NEXT:  // %bb.2: // %while.end
 ; CHECK-O2-NEXT:    mov w0, w8