[PATCH] D142546: [ConstraintElimination] Decompose or instruction if the constant operand < 2^known_zero_bits of the first operand.

[Zain Jaffal via Phabricator via llvm-commits]

zjaffal updated this revision to Diff 503016.
zjaffal marked 3 inline comments as done.
zjaffal added a comment.

- Add comment to explain that the operation is being treated as an add
- Address nit comments


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142546/new/

https://reviews.llvm.org/D142546

Files:
  llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
  llvm/test/Transforms/ConstraintElimination/or.ll


Index: llvm/test/Transforms/ConstraintElimination/or.ll
===================================================================
--- llvm/test/Transforms/ConstraintElimination/or.ll
+++ llvm/test/Transforms/ConstraintElimination/or.ll
@@ -454,13 +454,13 @@
 ; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_1:%.*]] = or i8 [[START]], 1
 ; CHECK-NEXT:    [[T_1:%.*]] = icmp ult i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_1]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_2:%.*]] = or i8 [[START]], 2
 ; CHECK-NEXT:    [[T_2:%.*]] = icmp ult i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_2]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_3:%.*]] = or i8 [[START]], 3
 ; CHECK-NEXT:    [[T_3:%.*]] = icmp ult i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_3]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_4:%.*]] = or i8 [[START]], 4
 ; CHECK-NEXT:    [[C_4:%.*]] = icmp ult i8 [[START_4]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[C_4]])
@@ -523,13 +523,13 @@
 ; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_1:%.*]] = or i8 [[START]], 1
 ; CHECK-NEXT:    [[T_1:%.*]] = icmp ule i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_1]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_2:%.*]] = or i8 [[START]], 2
 ; CHECK-NEXT:    [[T_2:%.*]] = icmp ule i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_2]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_3:%.*]] = or i8 [[START]], 3
 ; CHECK-NEXT:    [[T_3:%.*]] = icmp ule i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_3]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_4:%.*]] = or i8 [[START]], 4
 ; CHECK-NEXT:    [[T_4:%.*]] = icmp ule i8 [[START_4]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[T_4]])
@@ -599,13 +599,13 @@
 ; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_1:%.*]] = or i8 [[START]], 1
 ; CHECK-NEXT:    [[F_1:%.*]] = icmp ugt i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_1]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_2:%.*]] = or i8 [[START]], 2
 ; CHECK-NEXT:    [[F_2:%.*]] = icmp ugt i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_2]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_3:%.*]] = or i8 [[START]], 3
 ; CHECK-NEXT:    [[F_3:%.*]] = icmp ugt i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_3]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_4:%.*]] = or i8 [[START]], 4
 ; CHECK-NEXT:    [[F_4:%.*]] = icmp ugt i8 [[START_4]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[F_4]])
@@ -674,13 +674,13 @@
 ; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_1:%.*]] = or i8 [[START]], 1
 ; CHECK-NEXT:    [[F_1:%.*]] = icmp uge i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_1]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_2:%.*]] = or i8 [[START]], 2
 ; CHECK-NEXT:    [[F_2:%.*]] = icmp uge i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_2]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_3:%.*]] = or i8 [[START]], 3
 ; CHECK-NEXT:    [[F_3:%.*]] = icmp uge i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_3]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_4:%.*]] = or i8 [[START]], 4
 ; CHECK-NEXT:    [[C_4:%.*]] = icmp uge i8 [[START_4]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[C_4]])
Index: llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -32,6 +32,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/DebugCounter.h"
+#include "llvm/Support/KnownBits.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/Transforms/Utils/ValueMapper.h"
@@ -369,6 +370,12 @@
     return MergeResults(Op0, CI, true);
   }
 
+  // Decompose or as an add if there are no common bits between the operands.
+  if (match(V, m_Or(m_Value(Op0), m_ConstantInt(CI))) &&
+      haveNoCommonBitsSet(Op0, CI, DL)) {
+    return MergeResults(Op0, CI, IsSigned);
+  }
+
   if (match(V, m_NUWShl(m_Value(Op1), m_ConstantInt(CI))) && canUseSExt(CI)) {
     int64_t Mult = int64_t(std::pow(int64_t(2), CI->getSExtValue()));
     auto Result = decompose(Op1, Preconditions, IsSigned, DL);


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