[PATCH] D34921: [ConstantHoisting] Remove dupliate logic in constant hoisting

[Leo Li via Phabricator via llvm-commits]

aoli updated this revision to Diff 105505.
aoli added a comment.

Remove alloca check in constant hoisting.


https://reviews.llvm.org/D34921

Files:
  lib/Transforms/Scalar/ConstantHoisting.cpp
  test/Transforms/ConstantHoisting/ARM/insertvalue.ll


Index: test/Transforms/ConstantHoisting/ARM/insertvalue.ll
===================================================================
--- /dev/null
+++ test/Transforms/ConstantHoisting/ARM/insertvalue.ll
@@ -0,0 +1,31 @@
+; RUN: opt -consthoist -S < %s | FileCheck %s
+target triple = "thumbv6m-none-eabi"
+
+%T = type { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32 }
+
+; The second operand of insertvalue is able to be hoisted.
+define void @test1(%T %P) {
+; CHECK-LABEL:  @test1
+; CHECK:        %const = bitcast i32 256 to i32
+; CHECK:        %1 = insertvalue %T %P, i32 %const, 256
+; CHECK:        %2 = insertvalue %T %P, i32 %const, 256
+  %1 = insertvalue %T %P, i32 256, 256
+  %2 = insertvalue %T %P, i32 256, 256
+  ret void
+}
Index: lib/Transforms/Scalar/ConstantHoisting.cpp
===================================================================
--- lib/Transforms/Scalar/ConstantHoisting.cpp
+++ lib/Transforms/Scalar/ConstantHoisting.cpp
@@ -44,6 +44,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
 #include <tuple>
 
 using namespace llvm;
@@ -397,37 +398,15 @@
     if (isa<InlineAsm>(Call->getCalledValue()))
       return;
 
-  // Switch cases must remain constant, and if the value being tested is
-  // constant the entire thing should disappear.
-  if (isa<SwitchInst>(Inst))
-    return;
-
-  // Static allocas (constant size in the entry block) are handled by
-  // prologue/epilogue insertion so they're free anyway. We definitely don't
-  // want to make them non-constant.
-  auto AI = dyn_cast<AllocaInst>(Inst);
-  if (AI && AI->isStaticAlloca())
-    return;
-
-  // Constants in GEPs that index into a struct type should not be hoisted.
-  if (isa<GetElementPtrInst>(Inst)) {
-    gep_type_iterator GTI = gep_type_begin(Inst);
-
-    // Collect constant for first operand.
-    collectConstantCandidates(ConstCandMap, Inst, 0);
-    // Scan rest operands.
-    for (unsigned Idx = 1, E = Inst->getNumOperands(); Idx != E; ++Idx, ++GTI) {
-      // Only collect constants that index into a non struct type.
-      if (!GTI.isStruct()) {
-        collectConstantCandidates(ConstCandMap, Inst, Idx);
-      }
-    }
-    return;
-  }
-
   // Scan all operands.
   for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
-    collectConstantCandidates(ConstCandMap, Inst, Idx);
+    // The cost of materializing the constants (defined in
+    // `TargetTransformInfo::getIntImmCost`) for instructions which only take
+    // constant variables is lower than `TargetTransformInfo::TCC_Basic`. So
+    // it's safe for us to collect constant candidates from all IntrinsicInsts.
+    if (canReplaceOperandWithVariable(Inst, Idx) || isa<IntrinsicInst>(Inst)) {
+      collectConstantCandidates(ConstCandMap, Inst, Idx);
+    }
   } // end of for all operands
 }
 


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