[PATCH] D106677: [LV] Don't let ForceTargetInstructionCost override Invalid cost.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen created this revision.
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Invalid costs can be used to avoid vectorization with a given VF, which is
used for scalable vectors to avoid things that the code-generator cannot
handle. If we override the cost using the -force-target-instruction-cost
option of the LV, we would override this mechanism, rendering the flag useless.

This change ensures the cost is only overriden when the original cost that
was calculated is valid. That allows the flag to be used in combination
with the -scalable-vectorization option.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D106677

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll


Index: llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll
+++ llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll
@@ -1,6 +1,9 @@
 ; RUN: opt -S -loop-vectorize -force-vector-interleave=1 -instcombine -mattr=+sve -mtriple aarch64-unknown-linux-gnu -scalable-vectorization=on \
 ; RUN:     -pass-remarks-missed=loop-vectorize < %s 2>%t | FileCheck %s
 ; RUN: cat %t | FileCheck %s --check-prefix=CHECK-REMARKS
+; RUN: opt -S -loop-vectorize -force-vector-interleave=1 -force-target-instruction-cost=1 -instcombine -mattr=+sve -mtriple aarch64-unknown-linux-gnu \
+; RUN:     -scalable-vectorization=on -pass-remarks-missed=loop-vectorize < %s 2>%t | FileCheck %s
+; RUN: cat %t | FileCheck %s --check-prefix=CHECK-REMARKS
 
 define void @vec_load(i64 %N, double* nocapture %a, double* nocapture readonly %b) {
 ; CHECK-LABEL: @vec_load
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6895,7 +6895,8 @@
       VectorizationCostTy C = getInstructionCost(&I, VF);
 
       // Check if we should override the cost.
-      if (ForceTargetInstructionCost.getNumOccurrences() > 0)
+      if (C.first.isValid() &&
+          ForceTargetInstructionCost.getNumOccurrences() > 0)
         C.first = InstructionCost(ForceTargetInstructionCost);
 
       // Keep a list of instructions with invalid costs.


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