[llvm-commits] [llvm] r126635 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCompares.cpp test/Transforms/InstCombine/icmp.ll

[Nick Lewycky]

Author: nicholas
Date: Mon Feb 28 00:20:05 2011
New Revision: 126635

URL: http://llvm.org/viewvc/llvm-project?rev=126635&view=rev
Log:
The sign of an srem instruction is the sign of its dividend (the first
argument), regardless of the divisor. Teach instcombine about this and fix
test7 in PR9343!

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/icmp.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=126635&r1=126634&r2=126635&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Mon Feb 28 00:20:05 2011
@@ -1340,6 +1340,16 @@
       }
     }
     break;
+
+  case Instruction::SRem: {
+    bool TrueIfSigned;
+    if (LHSI->hasOneUse() &&
+        isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) {
+      // srem has the same sign as its dividend so the divisor is irrelevant.
+      return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), RHS);
+    }
+    break;
+  }
   }
   
   // Simplify icmp_eq and icmp_ne instructions with integer constant RHS.
@@ -1855,11 +1865,11 @@
       return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
                           ConstantInt::get(CI->getContext(), CI->getValue()+1));
     case ICmpInst::ICMP_UGE:
-      assert(!CI->isMinValue(false));                  // A >=u MIN -> TRUE
+      assert(!CI->isMinValue(false));                 // A >=u MIN -> TRUE
       return new ICmpInst(ICmpInst::ICMP_UGT, Op0,
                           ConstantInt::get(CI->getContext(), CI->getValue()-1));
     case ICmpInst::ICMP_SGE:
-      assert(!CI->isMinValue(true));                   // A >=s MIN -> TRUE
+      assert(!CI->isMinValue(true));                  // A >=s MIN -> TRUE
       return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
                           ConstantInt::get(CI->getContext(), CI->getValue()-1));
     }
@@ -1913,7 +1923,7 @@
                           ConstantInt::get(I.getContext(), Op1Min));
 
     // Based on the range information we know about the LHS, see if we can
-    // simplify this comparison.  For example, (x&4) < 8  is always true.
+    // simplify this comparison.  For example, (x&4) < 8 is always true.
     switch (I.getPredicate()) {
     default: llvm_unreachable("Unknown icmp opcode!");
     case ICmpInst::ICMP_EQ: {

Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=126635&r1=126634&r2=126635&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Mon Feb 28 00:20:05 2011
@@ -377,3 +377,13 @@
   %c = icmp ugt i32 %lhs, %rhs
   ret i1 %c
 }
+
+; PR9343 #7
+; CHECK: @test39
+; CHECK: ret i1 false
+define i1 @test39(i31 %X, i32 %Y) {
+  %A = zext i31 %X to i32
+  %B = srem i32 %A, %Y
+  %C = icmp slt i32 %B, 0
+  ret i1 %C
+}