[IVDescriptor] Explicitly check for isMinMaxRecurrenceKind in getReductionOpChain. NFC

[lukel97]

There are other types of recurrences with an icmp/fcmp opcode, AnyOf and FindLastIV, so don't rely on the opcode to detect them.
This makes adding support for AnyOf in #131830 easier.

Note that these currently fail the ExpectedUses/isCorrectOpcode checks anyway, so there shouldn't be any functional change.

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Luke Lau (lukel97)

Changes

There are other types of recurrences with an icmp/fcmp opcode, AnyOf and FindLastIV, so don't rely on the opcode to detect them.
This makes adding support for AnyOf in #131830 easier.

Note that these currently fail the ExpectedUses/isCorrectOpcode checks anyway, so there shouldn't be any functional change.

---

Full diff: https://github.com/llvm/llvm-project/pull/132025.diff

1 Files Affected:

• (modified) llvm/lib/Analysis/IVDescriptors.cpp (+3-3)

diff --git a/llvm/lib/Analysis/IVDescriptors.cpp b/llvm/lib/Analysis/IVDescriptors.cpp
index f74ede4450ce5..0b7f32e55faa5 100644
--- a/llvm/lib/Analysis/IVDescriptors.cpp
+++ b/llvm/lib/Analysis/IVDescriptors.cpp
@@ -1184,7 +1184,7 @@ RecurrenceDescriptor::getReductionOpChain(PHINode *Phi, Loop *L) const {
   // more expensive than out-of-loop reductions, and need to be costed more
   // carefully.
   unsigned ExpectedUses = 1;
-  if (RedOp == Instruction::ICmp || RedOp == Instruction::FCmp)
+  if (isMinMaxRecurrenceKind(Kind))
     ExpectedUses = 2;
 
   auto getNextInstruction = [&](Instruction *Cur) -> Instruction * {
@@ -1192,7 +1192,7 @@ RecurrenceDescriptor::getReductionOpChain(PHINode *Phi, Loop *L) const {
       Instruction *UI = cast<Instruction>(User);
       if (isa<PHINode>(UI))
         continue;
-      if (RedOp == Instruction::ICmp || RedOp == Instruction::FCmp) {
+      if (isMinMaxRecurrenceKind(Kind)) {
         // We are expecting a icmp/select pair, which we go to the next select
         // instruction if we can. We already know that Cur has 2 uses.
         if (isa<SelectInst>(UI))
@@ -1204,7 +1204,7 @@ RecurrenceDescriptor::getReductionOpChain(PHINode *Phi, Loop *L) const {
     return nullptr;
   };
   auto isCorrectOpcode = [&](Instruction *Cur) {
-    if (RedOp == Instruction::ICmp || RedOp == Instruction::FCmp) {
+    if (isMinMaxRecurrenceKind(Kind)) {
       Value *LHS, *RHS;
       return SelectPatternResult::isMinOrMax(
           matchSelectPattern(Cur, LHS, RHS).Flavor);

[david-arm]

Instead of recalculating this each time, is it perhaps better to calculate it once and store it in a variable for reuse?

[Mel-Chen]

LGTM, but please address David's comment before merging.

[fhahn]

LGTM, thanks