[PATCH] D74825: SpeculativeExecution: fixed ingoring free execution

[Daniil Fukalov via Phabricator via llvm-commits]

dfukalov created this revision.
dfukalov added reviewers: arsenm, chandlerc.
Herald added subscribers: kerbowa, hiraditya, tpr, nhaehnle, wdng, jvesely.
Herald added a project: LLVM.

After updating cost model in AMDGPU target (47a5c36b37f0 <https://reviews.llvm.org/rG47a5c36b37f033496de01b48cef0b2f1903c33cc>) the pass started to
ignore some BBs since they got all instructions estimated as free.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74825

Files:
  llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
  llvm/test/CodeGen/AMDGPU/speculative-execution-freecasts.ll


Index: llvm/test/CodeGen/AMDGPU/speculative-execution-freecasts.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AMDGPU/speculative-execution-freecasts.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -S -mtriple=amdgcn-unknown-amdhsa -speculative-execution \
+; RUN:   -spec-exec-max-speculation-cost 4 -spec-exec-max-not-hoisted 3 \
+; RUN:   | FileCheck %s
+
+; CHECK-LABEL: @ifThen_bitcast(
+; CHECK: bitcast
+; CHECK: br i1 true
+define void @ifThen_bitcast() {
+  br i1 true, label %a, label %b
+
+a:
+  %x = bitcast i32 undef to float
+  br label %b
+
+b:
+  ret void
+}
+
+; CHECK-LABEL: @ifThen_addrspacecast(
+; CHECK: addrspacecast
+; CHECK: br i1 true
+define void @ifThen_addrspacecast() {
+  br i1 true, label %a, label %b
+a:
+  %x = addrspacecast i32* undef to i32 addrspace(1)*
+  br label %b
+
+b:
+  ret void
+}
Index: llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
+++ llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
@@ -279,9 +279,6 @@
     }
   }
 
-  if (TotalSpeculationCost == 0)
-    return false; // nothing to hoist
-
   for (auto I = FromBlock.begin(); I != FromBlock.end();) {
     // We have to increment I before moving Current as moving Current
     // changes the list that I is iterating through.


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