[PATCH] D28780: [ValueTracking] Extend known bits to understand @llvm.bitreverse.

[Chad Rosier via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL292233: [ValueTracking] Extend known bits to understand @llvm.bitreverse. (authored by mcrosier).

Changed prior to commit:
  https://reviews.llvm.org/D28780?vs=84596&id=84688#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D28780

Files:
  llvm/trunk/lib/Analysis/ValueTracking.cpp
  llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll
  llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll


Index: llvm/trunk/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp
@@ -1400,6 +1400,11 @@
     if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
       switch (II->getIntrinsicID()) {
       default: break;
+      case Intrinsic::bitreverse:
+        computeKnownBits(I->getOperand(0), KnownZero2, KnownOne2, Depth + 1, Q);
+        KnownZero = KnownZero2.reverseBits();
+        KnownOne = KnownOne2.reverseBits();
+        break;
       case Intrinsic::bswap:
         computeKnownBits(I->getOperand(0), KnownZero2, KnownOne2, Depth + 1, Q);
         KnownZero |= KnownZero2.byteSwap();
Index: llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll
+++ llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll
@@ -0,0 +1,34 @@
+; RUN: opt < %s -S -instcombine | FileCheck %s
+
+declare i32 @llvm.bitreverse.i32(i32)
+
+; CHECK-LABEL: @test1
+; CHECK: ret i1 true
+define i1 @test1(i32 %arg) {
+  %a = or i32 %arg, 4294901760
+  %b = call i32 @llvm.bitreverse.i32(i32 %a)
+  %and = and i32 %b, 65535
+  %res = icmp eq i32 %and, 65535
+  ret i1 %res
+}
+
+; CHECK-LABEL: @test2
+; CHECK: ret i1 true
+define i1 @test2(i32 %arg) {
+  %a = or i32 %arg, 1
+  %b = call i32 @llvm.bitreverse.i32(i32 %a)
+  %c = and i32 %b, 2147483648
+  %d = call i32 @llvm.bitreverse.i32(i32 %c)
+  %res = icmp eq i32 %d, 1
+  ret i1 %res
+}
+
+; CHECK-LABEL: @test3
+; CHECK: ret i1 false
+define i1 @test3(i32 %arg) {
+  %a = or i32 %arg, 65536
+  %b = call i32 @llvm.bitreverse.i32(i32 %a)
+  %and = and i32 %b, 32768
+  %res = icmp eq i32 %and, 0
+  ret i1 %res
+}
Index: llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll
===================================================================
--- llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll
+++ llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll
@@ -0,0 +1,31 @@
+; RUN: opt < %s -S -instsimplify | FileCheck %s
+
+declare i32 @llvm.bitreverse.i32(i32)
+
+; CHECK-LABEL: @test1(
+; CHECK: ret i1 false
+define i1 @test1(i32 %arg) {
+  %a = or i32 %arg, 1
+  %b = call i32 @llvm.bitreverse.i32(i32 %a)
+  %res = icmp eq i32 %b, 0
+  ret i1 %res
+}
+
+; CHECK-LABEL: @test2(
+; CHECK: ret i1 false
+define i1 @test2(i32 %arg) {
+  %a = or i32 %arg, 1024
+  %b = call i32 @llvm.bitreverse.i32(i32 %a)
+  %res = icmp eq i32 %b, 0
+  ret i1 %res
+}
+
+; CHECK-LABEL: @test3(
+; CHECK: ret i1 false
+define i1 @test3(i32 %arg) {
+  %a = and i32 %arg, 1
+  %b = call i32 @llvm.bitreverse.i32(i32 %a)
+  %and = and i32 %b, 1
+  %res = icmp eq i32 %and, 1
+  ret i1 %res
+}


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