[InstCombine] Don't check uses of constant exprs (llvm#113684)

This patch skips constant expressions to avoid iterating over uses on
other functions.

Fix crash reported in
llvm#105510 (comment).

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -3753,7 +3753,9 @@ Instruction *InstCombinerImpl::visitBranchInst(BranchInst &BI) {
   }
 
   // Replace all dominated uses of the condition with true/false
-  if (BI.getSuccessor(0) != BI.getSuccessor(1)) {
+  // Ignore constant expressions to avoid iterating over uses on other
+  // functions.
+  if (!isa<Constant>(Cond) && BI.getSuccessor(0) != BI.getSuccessor(1)) {
     for (auto &U : make_early_inc_range(Cond->uses())) {
       BasicBlockEdge Edge0(BI.getParent(), BI.getSuccessor(0));
       if (DT.dominates(Edge0, U)) {

llvm/test/Transforms/InstCombine/pr105510.ll

@@ -0,0 +1,43 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+; Make sure we don't crash in this case.
+@g = global i32 0
+
+define i1 @foo() {
+; CHECK-LABEL: define i1 @foo() {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    br i1 ptrtoint (ptr @g to i1), label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    ret i1 true
+; CHECK:       [[IF_ELSE]]:
+; CHECK-NEXT:    ret i1 false
+;
+entry:
+  br i1 ptrtoint (ptr @g to i1), label %if.then, label %if.else
+
+if.then:
+  ret i1 true
+
+if.else:
+  ret i1 false
+}
+
+define i1 @bar() {
+; CHECK-LABEL: define i1 @bar() {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    br i1 ptrtoint (ptr @g to i1), label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    ret i1 true
+; CHECK:       [[IF_ELSE]]:
+; CHECK-NEXT:    ret i1 false
+;
+entry:
+  br i1 ptrtoint (ptr @g to i1), label %if.then, label %if.else
+
+if.then:
+  ret i1 true
+
+if.else:
+  ret i1 false
+}