[LICM] Fix assert failure in no-allowspeculation mode

In this case the source GEP might not be hoisted even though it
has invariant operands. For now just bail out, but we might need
additional checks for AllowSpeculation in these special-case
reassociation folds.

Author: nikic

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -2514,8 +2514,12 @@ static bool hoistGEP(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
   if (!L.isLoopInvariant(SrcPtr) || !all_of(GEP->indices(), LoopInvariant))
     return false;
 
-  assert(!all_of(Src->indices(), LoopInvariant) &&
-         "Would have been hoisted already");
+  // This can only happen if !AllowSpeculation, otherwise this would already be
+  // handled.
+  // FIXME: Should we respect AllowSpeculation in these reassociation folds?
+  // The flag exists to prevent metadata dropping, which is not relevant here.
+  if (all_of(Src->indices(), LoopInvariant))
+    return false;
 
   // The swapped GEPs are inbounds if both original GEPs are inbounds
   // and the sign of the offsets is the same. For simplicity, only

llvm/test/Transforms/LICM/gep-reassociate.ll

@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
-; RUN: opt -S -passes=licm < %s | FileCheck %s
+; RUN: opt -S -passes=licm < %s | FileCheck %s --check-prefixes=CHECK,SPEC
+; RUN: opt -S -passes='licm<no-allowspeculation>' < %s | FileCheck %s --check-prefixes=CHECK,NOSPEC
 
 declare void @use(ptr)
 declare i32 @get.i32()
@@ -387,3 +388,55 @@ loop:
 exit:
   ret void
 }
+
+define void @src_already_invariant_speculation(ptr %ptr, i1 %c, i1 %c2, i64 %arg1, i64 %arg2) {
+; SPEC-LABEL: define void @src_already_invariant_speculation
+; SPEC-SAME: (ptr [[PTR:%.*]], i1 [[C:%.*]], i1 [[C2:%.*]], i64 [[ARG1:%.*]], i64 [[ARG2:%.*]]) {
+; SPEC-NEXT:  entry:
+; SPEC-NEXT:    [[PTR2:%.*]] = getelementptr i8, ptr [[PTR]], i64 [[ARG1]]
+; SPEC-NEXT:    [[PTR3:%.*]] = getelementptr i8, ptr [[PTR2]], i64 [[ARG2]]
+; SPEC-NEXT:    br label [[LOOP:%.*]]
+; SPEC:       loop:
+; SPEC-NEXT:    br i1 [[C2]], label [[IF:%.*]], label [[LATCH:%.*]]
+; SPEC:       if:
+; SPEC-NEXT:    call void @use(ptr [[PTR3]])
+; SPEC-NEXT:    br label [[LATCH]]
+; SPEC:       latch:
+; SPEC-NEXT:    br i1 [[C]], label [[LOOP]], label [[EXIT:%.*]]
+; SPEC:       exit:
+; SPEC-NEXT:    ret void
+;
+; NOSPEC-LABEL: define void @src_already_invariant_speculation
+; NOSPEC-SAME: (ptr [[PTR:%.*]], i1 [[C:%.*]], i1 [[C2:%.*]], i64 [[ARG1:%.*]], i64 [[ARG2:%.*]]) {
+; NOSPEC-NEXT:  entry:
+; NOSPEC-NEXT:    br label [[LOOP:%.*]]
+; NOSPEC:       loop:
+; NOSPEC-NEXT:    br i1 [[C2]], label [[IF:%.*]], label [[LATCH:%.*]]
+; NOSPEC:       if:
+; NOSPEC-NEXT:    [[PTR2:%.*]] = getelementptr i8, ptr [[PTR]], i64 [[ARG1]]
+; NOSPEC-NEXT:    [[PTR3:%.*]] = getelementptr i8, ptr [[PTR2]], i64 [[ARG2]]
+; NOSPEC-NEXT:    call void @use(ptr [[PTR3]])
+; NOSPEC-NEXT:    br label [[LATCH]]
+; NOSPEC:       latch:
+; NOSPEC-NEXT:    br i1 [[C]], label [[LOOP]], label [[EXIT:%.*]]
+; NOSPEC:       exit:
+; NOSPEC-NEXT:    ret void
+;
+entry:
+  br label %loop
+
+loop:
+  br i1 %c2, label %if, label %latch
+
+if:
+  %ptr2 = getelementptr i8, ptr %ptr, i64 %arg1
+  %ptr3 = getelementptr i8, ptr %ptr2, i64 %arg2
+  call void @use(ptr %ptr3)
+  br label %latch
+
+latch:
+  br i1 %c, label %loop, label %exit
+
+exit:
+  ret void
+}