Index: lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2646,7 +2646,8 @@
     Changed = true;
   }
 
-  if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC))
+  if (Value *V =
+          SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC, &I))
     return ReplaceInstUsesWith(I, V);
 
   // comparing -val or val with non-zero is the same as just comparing val
@@ -3927,7 +3928,8 @@
 
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 
-  if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC))
+  if (Value *V =
+          SimplifyFCmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC, &I))
     return ReplaceInstUsesWith(I, V);
 
   // Simplify 'fcmp pred X, X'
Index: test/Transforms/InstCombine/pr23809.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/pr23809.ll
@@ -0,0 +1,22 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; InstCombine should preserve the call to @llvm.assume.
+define i32 @icmp(i32 %a, i32 %b) {
+; CHECK-LABEL: @icmp(
+  %sum = add i32 %a, %b
+  %1 = icmp sge i32 %sum, 0
+  call void @llvm.assume(i1 %1)
+; CHECK: call void @llvm.assume
+  ret i32 %sum
+}
+
+define float @fcmp(float %a, float %b) {
+; CHECK-LABEL: @fcmp(
+  %sum = fadd float %a, %b
+  %1 = fcmp oge float %sum, 0.0
+  call void @llvm.assume(i1 %1)
+; CHECK: call void @llvm.assume
+  ret float %sum
+}
+
+declare void @llvm.assume(i1)