[clang] f6875c4 - Reapply [IRBuilder] Always respect inserter/folder
Nikita Popov via cfe-commits
cfe-commits at lists.llvm.org
Wed Feb 19 12:02:39 PST 2020
Author: Nikita Popov
Date: 2020-02-19T20:51:38+01:00
New Revision: f6875c434ec20eb4f24495317592f64334347784
URL: https://github.com/llvm/llvm-project/commit/f6875c434ec20eb4f24495317592f64334347784
DIFF: https://github.com/llvm/llvm-project/commit/f6875c434ec20eb4f24495317592f64334347784.diff
LOG: Reapply [IRBuilder] Always respect inserter/folder
Some IRBuilder methods that were originally defined on
IRBuilderBase do not respect custom IRBuilder inserters/folders,
because those were not accessible prior to D73835. Fix this by
making use of existing (and now accessible) IRBuilder methods,
which will handle inserters/folders correctly.
There are some changes in OpenMP and Instrumentation tests, where
bitcasts now get constant folded. I've also highlighted one
InstCombine test which now finishes in two rather than three
iterations, thanks to new instructions being inserted into the
worklist.
Differential Revision: https://reviews.llvm.org/D74787
Added:
Modified:
clang/test/OpenMP/parallel_codegen.cpp
clang/test/OpenMP/target_firstprivate_codegen.cpp
llvm/lib/IR/IRBuilder.cpp
llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64.ll
llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64el.ll
llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64.ll
llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64le.ll
llvm/test/Instrumentation/MemorySanitizer/X86/vararg_call.ll
llvm/test/Instrumentation/MemorySanitizer/byval-alignment.ll
llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
llvm/test/Transforms/InstCombine/saturating-add-sub.ll
Removed:
################################################################################
diff --git a/clang/test/OpenMP/parallel_codegen.cpp b/clang/test/OpenMP/parallel_codegen.cpp
index f96ad406c25f..586187f09521 100644
--- a/clang/test/OpenMP/parallel_codegen.cpp
+++ b/clang/test/OpenMP/parallel_codegen.cpp
@@ -60,8 +60,7 @@ int main (int argc, char **argv) {
// ALL-DEBUG-LABEL: define i32 @main(i32 %argc, i8** %argv)
// CHECK-DEBUG: [[LOC_2_ADDR:%.+]] = alloca %struct.ident_t
// CHECK-DEBUG: [[KMPC_LOC_VOIDPTR:%.+]] = bitcast %struct.ident_t* [[LOC_2_ADDR]] to i8*
-// CHECK-DEBUG-NEXT: [[KMPC_DEFAULT_LOC_VOIDPTR:%.+]] = bitcast %struct.ident_t* [[DEF_LOC_2]] to i8*
-// CHECK-DEBUG-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[KMPC_LOC_VOIDPTR]], i8* align 8 [[KMPC_DEFAULT_LOC_VOIDPTR]], i64 24, i1 false)
+// CHECK-DEBUG-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[KMPC_LOC_VOIDPTR]], i8* align 8 bitcast (%struct.ident_t* [[DEF_LOC_2]] to i8*), i64 24, i1 false)
// ALL-DEBUG: store i32 %argc, i32* [[ARGC_ADDR:%.+]],
// ALL-DEBUG: [[VLA:%.+]] = alloca i32, i64 [[VLA_SIZE:%[^,]+]],
// CHECK-DEBUG: [[KMPC_LOC_PSOURCE_REF:%.+]] = getelementptr inbounds %struct.ident_t, %struct.ident_t* [[LOC_2_ADDR]], i32 0, i32 4
@@ -118,8 +117,7 @@ int main (int argc, char **argv) {
// ALL-DEBUG: define linkonce_odr i32 [[TMAIN]](i8** %argc)
// CHECK-DEBUG-DAG: [[LOC_2_ADDR:%.+]] = alloca %struct.ident_t
// CHECK-DEBUG: [[KMPC_LOC_VOIDPTR:%.+]] = bitcast %struct.ident_t* [[LOC_2_ADDR]] to i8*
-// CHECK-DEBUG-NEXT: [[KMPC_DEFAULT_LOC_VOIDPTR:%.+]] = bitcast %struct.ident_t* [[DEF_LOC_2]] to i8*
-// CHECK-DEBUG-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[KMPC_LOC_VOIDPTR]], i8* align 8 [[KMPC_DEFAULT_LOC_VOIDPTR]], i64 24, i1 false)
+// CHECK-DEBUG-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[KMPC_LOC_VOIDPTR]], i8* align 8 bitcast (%struct.ident_t* [[DEF_LOC_2]] to i8*), i64 24, i1 false)
// CHECK-DEBUG-NEXT: store i8** %argc, i8*** [[ARGC_ADDR:%.+]],
// CHECK-DEBUG: [[KMPC_LOC_PSOURCE_REF:%.+]] = getelementptr inbounds %struct.ident_t, %struct.ident_t* [[LOC_2_ADDR]], i32 0, i32 4
// CHECK-DEBUG-NEXT: store i8* getelementptr inbounds ([{{.+}} x i8], [{{.+}} x i8]* [[LOC2]], i32 0, i32 0), i8** [[KMPC_LOC_PSOURCE_REF]]
diff --git a/clang/test/OpenMP/target_firstprivate_codegen.cpp b/clang/test/OpenMP/target_firstprivate_codegen.cpp
index 0b5f5f9b2b17..b90ab42f5ae2 100644
--- a/clang/test/OpenMP/target_firstprivate_codegen.cpp
+++ b/clang/test/OpenMP/target_firstprivate_codegen.cpp
@@ -336,9 +336,8 @@ int foo(int n, double *ptr) {
}
// CHECK: [[PTR_ADDR_REF:%.+]] = load double*, double** [[PTR_ADDR]],
- // CHECK: [[FP_E_BC:%.+]] = bitcast [[TTII]]* [[FP_E]] to i8*
// CHECK: [[E_BC:%.+]] = bitcast [[TTII]]* [[E:%.+]] to i8*
- // CHECK: call void @llvm.memcpy.p0i8.p0i8.i{{64|32}}(i8* {{.*}} [[FP_E_BC]], i8* {{.*}} [[E_BC]], i{{64|32}} 8, i1 false)
+ // CHECK: call void @llvm.memcpy.p0i8.p0i8.i{{64|32}}(i8* {{.*}} bitcast ([[TTII]]* [[FP_E]] to i8*), i8* {{.*}} [[E_BC]], i{{64|32}} 8, i1 false)
// CHECK: [[BASE_PTR_GEP3_0:%.+]] = getelementptr inbounds [2 x i8*], [2 x i8*]* [[BASE_PTR_ARR3]], i{{[0-9]+}} 0, i{{[0-9]+}} 0
// CHECK: [[BCAST_TOPTR:%.+]] = bitcast i8** [[BASE_PTR_GEP3_0]] to double**
// CHECK: store double* [[PTR_ADDR_REF]], double** [[BCAST_TOPTR]],
diff --git a/llvm/lib/IR/IRBuilder.cpp b/llvm/lib/IR/IRBuilder.cpp
index 457255b157cc..71cf2c04d1d0 100644
--- a/llvm/lib/IR/IRBuilder.cpp
+++ b/llvm/lib/IR/IRBuilder.cpp
@@ -65,38 +65,19 @@ Value *IRBuilderBase::getCastedInt8PtrValue(Value *Ptr) {
return Ptr;
// Otherwise, we need to insert a bitcast.
- PT = getInt8PtrTy(PT->getAddressSpace());
- BitCastInst *BCI = new BitCastInst(Ptr, PT, "");
- BB->getInstList().insert(InsertPt, BCI);
- SetInstDebugLocation(BCI);
- return BCI;
+ return CreateBitCast(Ptr, getInt8PtrTy(PT->getAddressSpace()));
}
static CallInst *createCallHelper(Function *Callee, ArrayRef<Value *> Ops,
IRBuilderBase *Builder,
const Twine &Name = "",
Instruction *FMFSource = nullptr) {
- CallInst *CI = CallInst::Create(Callee, Ops, Name);
+ CallInst *CI = Builder->CreateCall(Callee, Ops, Name);
if (FMFSource)
CI->copyFastMathFlags(FMFSource);
- Builder->GetInsertBlock()->getInstList().insert(Builder->GetInsertPoint(),CI);
- Builder->SetInstDebugLocation(CI);
return CI;
}
-static InvokeInst *createInvokeHelper(Function *Invokee, BasicBlock *NormalDest,
- BasicBlock *UnwindDest,
- ArrayRef<Value *> Ops,
- IRBuilderBase *Builder,
- const Twine &Name = "") {
- InvokeInst *II =
- InvokeInst::Create(Invokee, NormalDest, UnwindDest, Ops, Name);
- Builder->GetInsertBlock()->getInstList().insert(Builder->GetInsertPoint(),
- II);
- Builder->SetInstDebugLocation(II);
- return II;
-}
-
CallInst *IRBuilderBase::CreateMemSet(Value *Ptr, Value *Val, Value *Size,
MaybeAlign Align, bool isVolatile,
MDNode *TBAATag, MDNode *ScopeTag,
@@ -696,8 +677,8 @@ static InvokeInst *CreateGCStatepointInvokeCommon(
std::vector<Value *> Args =
getStatepointArgs(*Builder, ID, NumPatchBytes, ActualInvokee, Flags,
InvokeArgs, TransitionArgs, DeoptArgs, GCArgs);
- return createInvokeHelper(FnStatepoint, NormalDest, UnwindDest, Args, Builder,
- Name);
+ return Builder->CreateInvoke(FnStatepoint, NormalDest, UnwindDest, Args,
+ Name);
}
InvokeInst *IRBuilderBase::CreateGCStatepointInvoke(
diff --git a/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64.ll b/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64.ll
index 03d1fda5eda6..97755c72881e 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64.ll
@@ -21,8 +21,7 @@ define i32 @foo(i32 %guard, ...) {
; CHECK: [[B:%.*]] = add i64 0, [[A]]
; CHECK: [[C:%.*]] = alloca {{.*}} [[B]]
-; CHECK: [[STACK:%.*]] = bitcast {{.*}} @__msan_va_arg_tls to i8*
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 [[STACK]], i64 [[B]], i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 bitcast ({{.*}} @__msan_va_arg_tls to i8*), i64 [[B]], i1 false)
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
declare void @llvm.va_start(i8*) #2
diff --git a/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64el.ll b/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64el.ll
index 98b1d8211023..0508c428ef75 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64el.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/Mips/vararg-mips64el.ll
@@ -21,8 +21,7 @@ define i32 @foo(i32 %guard, ...) {
; CHECK: [[B:%.*]] = add i64 0, [[A]]
; CHECK: [[C:%.*]] = alloca {{.*}} [[B]]
-; CHECK: [[STACK:%.*]] = bitcast {{.*}} @__msan_va_arg_tls to i8*
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 [[STACK]], i64 [[B]], i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 bitcast ({{.*}} @__msan_va_arg_tls to i8*), i64 [[B]], i1 false)
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
declare void @llvm.va_start(i8*) #2
diff --git a/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64.ll b/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64.ll
index 9e74752bcd50..36da7add8801 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64.ll
@@ -21,8 +21,7 @@ define i32 @foo(i32 %guard, ...) {
; CHECK: [[B:%.*]] = add i64 0, [[A]]
; CHECK: [[C:%.*]] = alloca {{.*}} [[B]]
-; CHECK: [[STACK:%.*]] = bitcast {{.*}} @__msan_va_arg_tls to i8*
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 [[STACK]], i64 [[B]], i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 bitcast ({{.*}} @__msan_va_arg_tls to i8*), i64 [[B]], i1 false)
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
declare void @llvm.va_start(i8*) #2
@@ -98,8 +97,7 @@ define i32 @bar6([2 x i64]* %arg) {
}
; CHECK-LABEL: @bar6
-; CHECK: [[SHADOW:%[0-9]+]] = bitcast [2 x i64]* bitcast ([100 x i64]* @__msan_va_arg_tls to [2 x i64]*) to i8*
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[SHADOW]], i8* align 8 {{.*}}, i64 16, i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 bitcast ([100 x i64]* @__msan_va_arg_tls to i8*), i8* align 8 {{.*}}, i64 16, i1 false)
; CHECK: store {{.*}} 16, {{.*}} @__msan_va_arg_overflow_size_tls
; Check 16-aligned byval.
@@ -109,8 +107,7 @@ define i32 @bar7([4 x i64]* %arg) {
}
; CHECK-LABEL: @bar7
-; CHECK: [[SHADOW:%[0-9]+]] = bitcast [4 x i64]* inttoptr (i64 add (i64 ptrtoint ([100 x i64]* @__msan_va_arg_tls to i64), i64 8) to [4 x i64]*)
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[SHADOW]], i8* align 8 {{.*}}, i64 32, i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 inttoptr (i64 add (i64 ptrtoint ([100 x i64]* @__msan_param_tls to i64), i64 8) to i8*), i8* align 8 {{.*}}, i64 32, i1 false)
; CHECK: store {{.*}} 40, {{.*}} @__msan_va_arg_overflow_size_tls
diff --git a/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64le.ll b/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64le.ll
index 9d6c43657ed6..ac8df55fee48 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64le.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/PowerPC/vararg-ppc64le.ll
@@ -21,8 +21,7 @@ define i32 @foo(i32 %guard, ...) {
; CHECK: [[B:%.*]] = add i64 0, [[A]]
; CHECK: [[C:%.*]] = alloca {{.*}} [[B]]
-; CHECK: [[STACK:%.*]] = bitcast {{.*}} @__msan_va_arg_tls to i8*
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 [[STACK]], i64 [[B]], i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[C]], i8* align 8 bitcast ({{.*}} @__msan_va_arg_tls to i8*), i64 [[B]], i1 false)
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
declare void @llvm.va_start(i8*) #2
@@ -82,8 +81,7 @@ define i32 @bar6([2 x i64]* %arg) {
}
; CHECK-LABEL: @bar6
-; CHECK: [[SHADOW:%[0-9]+]] = bitcast [2 x i64]* bitcast ([100 x i64]* @__msan_va_arg_tls to [2 x i64]*) to i8*
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[SHADOW]], i8* align 8 {{.*}}, i64 16, i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 bitcast ([100 x i64]* @__msan_va_arg_tls to i8*), i8* align 8 {{.*}}, i64 16, i1 false)
; CHECK: store {{.*}} 16, {{.*}} @__msan_va_arg_overflow_size_tls
; Check 16-aligned byval.
@@ -93,8 +91,7 @@ define i32 @bar7([4 x i64]* %arg) {
}
; CHECK-LABEL: @bar7
-; CHECK: [[SHADOW:%[0-9]+]] = bitcast [4 x i64]* inttoptr (i64 add (i64 ptrtoint ([100 x i64]* @__msan_va_arg_tls to i64), i64 8) to [4 x i64]*)
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[SHADOW]], i8* align 8 {{.*}}, i64 32, i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 inttoptr (i64 add (i64 ptrtoint ([100 x i64]* @__msan_param_tls to i64), i64 8) to i8*), i8* align 8 {{.*}}, i64 32, i1 false)
; CHECK: store {{.*}} 40, {{.*}} @__msan_va_arg_overflow_size_tls
; Test that MSan doesn't generate code overflowing __msan_va_arg_tls when too many arguments are
diff --git a/llvm/test/Instrumentation/MemorySanitizer/X86/vararg_call.ll b/llvm/test/Instrumentation/MemorySanitizer/X86/vararg_call.ll
index eea84451fb59..c815bdd22b8c 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/X86/vararg_call.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/X86/vararg_call.ll
@@ -42,10 +42,8 @@ entry:
%cmp9 = icmp sgt i32 %n, 0
br i1 %cmp9, label %for.body.lr.ph, label %for.end
-; CHECK: [[VA_ARG_TLS:%[_0-9a-z]+]] = bitcast {{.*}} @__msan_va_arg_tls
-; CHECK: call void @llvm.memcpy.{{.*}} [[SHADOW_COPY:%[_0-9a-z]+]], {{.*}} [[VA_ARG_TLS]]
-; CHECK-ORIGIN: [[VA_ARG_ORIGIN_TLS:%[_0-9a-z]+]] = bitcast {{.*}} @__msan_va_arg_origin_tls
-; CHECK-ORIGIN: call void @llvm.memcpy{{.*}} [[ORIGIN_COPY:%[_0-9a-z]+]], {{.*}} [[VA_ARG_ORIGIN_TLS]]
+; CHECK: call void @llvm.memcpy.{{.*}} [[SHADOW_COPY:%[_0-9a-z]+]], {{.*}} bitcast ({{.*}} @__msan_va_arg_tls to i8*)
+; CHECK-ORIGIN: call void @llvm.memcpy{{.*}} [[ORIGIN_COPY:%[_0-9a-z]+]], {{.*}} bitcast ({{.*}} @__msan_va_arg_origin_tls to i8*)
; CHECK: call void @llvm.va_start
; CHECK: call void @llvm.memcpy.{{.*}}, {{.*}} [[SHADOW_COPY]], i{{.*}} [[REGSAVE:[0-9]+]]
diff --git a/llvm/test/Instrumentation/MemorySanitizer/byval-alignment.ll b/llvm/test/Instrumentation/MemorySanitizer/byval-alignment.ll
index 0d5da362f34c..acf9c27fb5be 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/byval-alignment.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/byval-alignment.ll
@@ -9,8 +9,7 @@ target triple = "x86_64-unknown-linux-gnu"
%struct.S = type { i64, i64, i64, [8 x i8] }
-; CHECK: [[A:%.*]] = bitcast i64* {{.*}} add {{.*}} ptrtoint {{.*}} @__msan_param_tls {{.*}} i64 8)
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[A]], i8* align 8 {{.*}}, i64 32, i1 false)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 {{.*}} add {{.*}} ptrtoint {{.*}} @__msan_param_tls {{.*}} i64 8) {{.*}}, i8* align 8 {{.*}}, i64 32, i1 false)
define void @Caller() sanitize_memory {
entry:
diff --git a/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll b/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
index f56233d13420..475c3e9f4542 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
@@ -929,8 +929,7 @@ entry:
; CHECK: store i64 {{.*}}, i64* {{.*}}@__msan_va_arg_tls{{.*}}, i64 32){{.*}}, align 8
; third struct through the overflow area byval
; CHECK: ptrtoint %struct.StructByVal* {{.*}} to i64
-; CHECK: bitcast { i32, i32, i32, i32 }* {{.*}}@__msan_va_arg_tls {{.*}}, i64 176
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64{{.*}}@__msan_va_arg_tls {{.*}}, i64 176
; CHECK: store i64 16, i64* @__msan_va_arg_overflow_size_tls
; CHECK: call void (i32, ...) @VAArgStructFn
; CHECK: ret void
@@ -954,7 +953,7 @@ entry:
attributes #0 = { "target-features"="+fxsr,+x87,-sse" }
-; CHECK: bitcast { i32, i32, i32, i32 }* {{.*}}@__msan_va_arg_tls {{.*}}, i64 48
+; CHECK call void @llvm.memcpy.p0i8.p0i8.i64{{.*}}@__msan_va_arg_tls {{.*}}, i64 48
declare i32 @InnerTailCall(i32 %a)
diff --git a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
index 57ef7515e66c..7306bd42020e 100644
--- a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
+++ b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -instcombine -S | FileCheck %s
+; RUN: opt < %s -instcombine -instcombine-infinite-loop-threshold=2 -S | FileCheck %s
;
; Saturating addition.
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