[llvm] edf7004 - [ConstantFold] Handle vectors in ConstantFoldLoadThroughBitcast()

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2021-03-06T12:17:56+01:00
New Revision: edf7004851519464f86b0f641da4d6c9506decb1

URL: https://github.com/llvm/llvm-project/commit/edf7004851519464f86b0f641da4d6c9506decb1
DIFF: https://github.com/llvm/llvm-project/commit/edf7004851519464f86b0f641da4d6c9506decb1.diff

LOG: [ConstantFold] Handle vectors in ConstantFoldLoadThroughBitcast()

There seems to be an impedance mismatch between what the type
system considers an aggregate (structs and arrays) and what
constants consider an aggregate (structs, arrays and vectors).

Rather than adjusting the type check, simply drop it entirely,
as getAggregateElement() is well-defined for non-aggregates: It
simply returns null in that case.

Added: 
    

Modified: 
    llvm/lib/Analysis/ConstantFolding.cpp
    llvm/test/Transforms/GVN/non-integral-pointers-inseltpoison.ll
    llvm/test/Transforms/GVN/non-integral-pointers.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index f73890d548f0..f14b205ed148 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -387,11 +387,6 @@ Constant *llvm::ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy,
         return ConstantExpr::getCast(Cast, C, DestTy);
     }
 
-    // If this isn't an aggregate type, there is nothing we can do to drill down
-    // and find a bitcastable constant.
-    if (!SrcTy->isAggregateType())
-      return nullptr;
-
     // We're simulating a load through a pointer that was bitcast to point to
     // a 
diff erent type, so we can try to walk down through the initial
     // elements of an aggregate to see if some part of the aggregate is

diff  --git a/llvm/test/Transforms/GVN/non-integral-pointers-inseltpoison.ll b/llvm/test/Transforms/GVN/non-integral-pointers-inseltpoison.ll
index 2aef7620841b..d26003b2c8f2 100644
--- a/llvm/test/Transforms/GVN/non-integral-pointers-inseltpoison.ll
+++ b/llvm/test/Transforms/GVN/non-integral-pointers-inseltpoison.ll
@@ -213,14 +213,12 @@ entry:
   ret i64 addrspace(4)* %ref
 }
 
-; TODO: missed optimization
 define i8 addrspace(4)* @forward_memcopy(i8 addrspace(4)* addrspace(4)* %loc) {
 ; CHECK-LABEL: @forward_memcopy(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[LOC_BC:%.*]] = bitcast i8 addrspace(4)* addrspace(4)* [[LOC:%.*]] to i8 addrspace(4)*
 ; CHECK-NEXT:    call void @llvm.memcpy.p4i8.p0i8.i64(i8 addrspace(4)* align 4 [[LOC_BC]], i8* bitcast (<4 x i64 addrspace(4)*>* @NonZeroConstant2 to i8*), i64 8, i1 false)
-; CHECK-NEXT:    [[REF:%.*]] = load i8 addrspace(4)*, i8 addrspace(4)* addrspace(4)* [[LOC]], align 8
-; CHECK-NEXT:    ret i8 addrspace(4)* [[REF]]
+; CHECK-NEXT:    ret i8 addrspace(4)* bitcast (i64 addrspace(4)* getelementptr (i64, i64 addrspace(4)* null, i32 3) to i8 addrspace(4)*)
 ;
 entry:
   %loc.bc = bitcast i8 addrspace(4)* addrspace(4)* %loc to i8 addrspace(4)*

diff  --git a/llvm/test/Transforms/GVN/non-integral-pointers.ll b/llvm/test/Transforms/GVN/non-integral-pointers.ll
index 6b9a9171f5f3..07d941fdb619 100644
--- a/llvm/test/Transforms/GVN/non-integral-pointers.ll
+++ b/llvm/test/Transforms/GVN/non-integral-pointers.ll
@@ -213,14 +213,12 @@ entry:
   ret i64 addrspace(4)* %ref
 }
 
-; TODO: missed optimization
 define i8 addrspace(4)* @forward_memcopy(i8 addrspace(4)* addrspace(4)* %loc) {
 ; CHECK-LABEL: @forward_memcopy(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[LOC_BC:%.*]] = bitcast i8 addrspace(4)* addrspace(4)* [[LOC:%.*]] to i8 addrspace(4)*
 ; CHECK-NEXT:    call void @llvm.memcpy.p4i8.p0i8.i64(i8 addrspace(4)* align 4 [[LOC_BC]], i8* bitcast (<4 x i64 addrspace(4)*>* @NonZeroConstant2 to i8*), i64 8, i1 false)
-; CHECK-NEXT:    [[REF:%.*]] = load i8 addrspace(4)*, i8 addrspace(4)* addrspace(4)* [[LOC]], align 8
-; CHECK-NEXT:    ret i8 addrspace(4)* [[REF]]
+; CHECK-NEXT:    ret i8 addrspace(4)* bitcast (i64 addrspace(4)* getelementptr (i64, i64 addrspace(4)* null, i32 3) to i8 addrspace(4)*)
 ;
 entry:
   %loc.bc = bitcast i8 addrspace(4)* addrspace(4)* %loc to i8 addrspace(4)*