[llvm] r292233 - [ValueTracking] Extend known bits to understand @llvm.bitreverse.

[Chad Rosier via llvm-commits]

Author: mcrosier
Date: Tue Jan 17 11:23:51 2017
New Revision: 292233

URL: http://llvm.org/viewvc/llvm-project?rev=292233&view=rev
Log:
[ValueTracking] Extend known bits to understand @llvm.bitreverse.

Differential Revision: https://reviews.llvm.org/D28780

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

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=292233&r1=292232&r2=292233&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Jan 17 11:23:51 2017
@@ -1400,6 +1400,11 @@ static void computeKnownBitsFromOperator
     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();

Added: llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll?rev=292233&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/bitreverse-known-bits.ll Tue Jan 17 11:23:51 2017
@@ -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
+}

Added: llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll?rev=292233&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll (added)
+++ llvm/trunk/test/Transforms/InstSimplify/bitreverse.ll Tue Jan 17 11:23:51 2017
@@ -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
+}