[llvm-commits] [llvm] r143209 - in /llvm/trunk: lib/Analysis/InstructionSimplify.cpp test/Transforms/InstSimplify/compare.ll

[Duncan Sands]

Author: baldrick
Date: Fri Oct 28 13:17:44 2011
New Revision: 143209

URL: http://llvm.org/viewvc/llvm-project?rev=143209&view=rev
Log:
Fold icmp ugt (udiv X, Y), X to false.  Spotted by my super-optimizer
in 186.crafty.

Modified:
    llvm/trunk/lib/Analysis/InstructionSimplify.cpp
    llvm/trunk/test/Transforms/InstSimplify/compare.ll

Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=143209&r1=143208&r2=143209&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Fri Oct 28 13:17:44 2011
@@ -1574,6 +1574,9 @@
       // 'srem x, CI2' produces (-|CI2|, |CI2|).
       Upper = CI2->getValue().abs();
       Lower = (-Upper) + 1;
+    } else if (match(LHS, m_UDiv(m_ConstantInt(CI2), m_Value()))) {
+      // 'udiv CI2, x' produces [0, CI2].
+      Upper = CI2->getValue();
     } else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) {
       // 'udiv x, CI2' produces [0, UINT_MAX / CI2].
       APInt NegOne = APInt::getAllOnesValue(Width);
@@ -1880,6 +1883,15 @@
     }
   }
 
+  // x udiv y <=u x.
+  if (LBO && match(LBO, m_UDiv(m_Specific(RHS), m_Value()))) {
+    // icmp pred (X /u Y), X
+    if (Pred == ICmpInst::ICMP_UGT)
+      return getFalse(ITy);
+    if (Pred == ICmpInst::ICMP_ULE)
+      return getTrue(ITy);
+  }
+
   if (MaxRecurse && LBO && RBO && LBO->getOpcode() == RBO->getOpcode() &&
       LBO->getOperand(1) == RBO->getOperand(1)) {
     switch (LBO->getOpcode()) {

Modified: llvm/trunk/test/Transforms/InstSimplify/compare.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/compare.ll?rev=143209&r1=143208&r2=143209&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/compare.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/compare.ll Fri Oct 28 13:17:44 2011
@@ -300,6 +300,30 @@
 ; CHECK: ret i1 true
 }
 
+define i1 @udiv3(i32 %X, i32 %Y) {
+; CHECK: @udiv3
+  %A = udiv i32 %X, %Y
+  %C = icmp ugt i32 %A, %X
+  ret i1 %C
+; CHECK: ret i1 false
+}
+
+define i1 @udiv4(i32 %X, i32 %Y) {
+; CHECK: @udiv4
+  %A = udiv i32 %X, %Y
+  %C = icmp ule i32 %A, %X
+  ret i1 %C
+; CHECK: ret i1 true
+}
+
+define i1 @udiv5(i32 %X) {
+; CHECK: @udiv5
+  %A = udiv i32 123, %X
+  %C = icmp ugt i32 %A, 124
+  ret i1 %C
+; CHECK: ret i1 false
+}
+
 define i1 @sdiv1(i32 %X) {
 ; CHECK: @sdiv1
   %A = sdiv i32 %X, 1000000