[llvm] r343053 - Revert "Revert "[ConstHoist] Do not rebase single (or few) dependent constant""
Zhaoshi Zheng via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 25 17:59:09 PDT 2018
Author: zzheng
Date: Tue Sep 25 17:59:09 2018
New Revision: 343053
URL: http://llvm.org/viewvc/llvm-project?rev=343053&view=rev
Log:
Revert "Revert "[ConstHoist] Do not rebase single (or few) dependent constant""
This reverts commit bd7b44f35ee9fbe365eb25ce55437ea793b39346.
Reland r342994: disabled the optimization and explicitly enable it in test.
-mllvm -consthoist-min-num-to-rebase<unsigned>=0
[ConstHoist] Do not rebase single (or few) dependent constant
If an instance (InsertionPoint or IP) of Base constant A has only one or few
rebased constants depending on it, do NOT rebase. One extra ADD instruction is
required to materialize each rebased constant, assuming A and the rebased have
the same materialization cost.
Differential Revision: https://reviews.llvm.org/D52243
Added:
llvm/trunk/test/CodeGen/Thumb/consthoist-few-dependents.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp?rev=343053&r1=343052&r2=343053&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp Tue Sep 25 17:59:09 2018
@@ -86,6 +86,12 @@ static cl::opt<bool> ConstHoistGEP(
"consthoist-gep", cl::init(false), cl::Hidden,
cl::desc("Try hoisting constant gep expressions"));
+static cl::opt<unsigned>
+MinNumOfDependentToRebase("consthoist-min-num-to-rebase",
+ cl::desc("Do not rebase if number of dependent constants of a Base is less "
+ "than this number."),
+ cl::init(0), cl::Hidden);
+
namespace {
/// The constant hoisting pass.
@@ -822,7 +828,34 @@ bool ConstantHoistingPass::emitBaseConst
unsigned UsesNum = 0;
unsigned ReBasesNum = 0;
+ unsigned NotRebasedNum = 0;
for (Instruction *IP : IPSet) {
+ // First, collect constants depending on this IP of the base.
+ unsigned Uses = 0;
+ using RebasedUse = std::tuple<Constant *, Type *, ConstantUser>;
+ SmallVector<RebasedUse, 4> ToBeRebased;
+ for (auto const &RCI : ConstInfo.RebasedConstants) {
+ for (auto const &U : RCI.Uses) {
+ Uses++;
+ BasicBlock *OrigMatInsertBB =
+ findMatInsertPt(U.Inst, U.OpndIdx)->getParent();
+ // If Base constant is to be inserted in multiple places,
+ // generate rebase for U using the Base dominating U.
+ if (IPSet.size() == 1 ||
+ DT->dominates(IP->getParent(), OrigMatInsertBB))
+ ToBeRebased.push_back(RebasedUse(RCI.Offset, RCI.Ty, U));
+ }
+ }
+ UsesNum = Uses;
+
+ // If only few constants depend on this IP of base, skip rebasing,
+ // assuming the base and the rebased have the same materialization cost.
+ if (ToBeRebased.size() < MinNumOfDependentToRebase) {
+ NotRebasedNum += ToBeRebased.size();
+ continue;
+ }
+
+ // Emit an instance of the base at this IP.
Instruction *Base = nullptr;
// Hoist and hide the base constant behind a bitcast.
if (ConstInfo.BaseExpr) {
@@ -840,36 +873,27 @@ bool ConstantHoistingPass::emitBaseConst
<< ") to BB " << IP->getParent()->getName() << '\n'
<< *Base << '\n');
- // Emit materialization code for all rebased constants.
- unsigned Uses = 0;
- for (auto const &RCI : ConstInfo.RebasedConstants) {
- for (auto const &U : RCI.Uses) {
- Uses++;
- BasicBlock *OrigMatInsertBB =
- findMatInsertPt(U.Inst, U.OpndIdx)->getParent();
- // If Base constant is to be inserted in multiple places,
- // generate rebase for U using the Base dominating U.
- if (IPSet.size() == 1 ||
- DT->dominates(Base->getParent(), OrigMatInsertBB)) {
- emitBaseConstants(Base, RCI.Offset, RCI.Ty, U);
- ReBasesNum++;
- }
-
- Base->setDebugLoc(DILocation::getMergedLocation(
- Base->getDebugLoc(), U.Inst->getDebugLoc()));
- }
+ // Emit materialization code for rebased constants depending on this IP.
+ for (auto const &R : ToBeRebased) {
+ Constant *Off = std::get<0>(R);
+ Type *Ty = std::get<1>(R);
+ ConstantUser U = std::get<2>(R);
+ emitBaseConstants(Base, Off, Ty, U);
+ ReBasesNum++;
+ // Use the same debug location as the last user of the constant.
+ Base->setDebugLoc(DILocation::getMergedLocation(
+ Base->getDebugLoc(), U.Inst->getDebugLoc()));
}
- UsesNum = Uses;
-
- // Use the same debug location as the last user of the constant.
assert(!Base->use_empty() && "The use list is empty!?");
assert(isa<Instruction>(Base->user_back()) &&
"All uses should be instructions.");
}
(void)UsesNum;
(void)ReBasesNum;
+ (void)NotRebasedNum;
// Expect all uses are rebased after rebase is done.
- assert(UsesNum == ReBasesNum && "Not all uses are rebased");
+ assert(UsesNum == (ReBasesNum + NotRebasedNum) &&
+ "Not all uses are rebased");
NumConstantsHoisted++;
Added: llvm/trunk/test/CodeGen/Thumb/consthoist-few-dependents.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Thumb/consthoist-few-dependents.ll?rev=343053&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/Thumb/consthoist-few-dependents.ll (added)
+++ llvm/trunk/test/CodeGen/Thumb/consthoist-few-dependents.ll Tue Sep 25 17:59:09 2018
@@ -0,0 +1,191 @@
+; RUN: opt -consthoist -S %s -o - | FileCheck %s --check-prefix=OPT
+; RUN: opt -consthoist -S -consthoist-min-num-to-rebase=1 %s -o - | FileCheck %s --check-prefix=OPT --check-prefix=OPT-1
+; RUN: opt -consthoist -S -consthoist-min-num-to-rebase=2 %s -o - | FileCheck %s --check-prefix=OPT --check-prefix=OPT-2
+; RUN: opt -consthoist -S -consthoist-min-num-to-rebase=3 %s -o - | FileCheck %s --check-prefix=OPT --check-prefix=OPT-3
+
+; RUN: llc -consthoist-min-num-to-rebase=2 %s -o - | FileCheck %s --check-prefix=LLC
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv6m-none-unknown-musleabi"
+
+; Test that constant 0 and 1 of i1 type is NOT hoisted due low
+; materializing cost.
+
+; OPT-LABEL: avalon
+; OPT: bb1:
+; OPT: store i1 true
+; OPT: bb2:
+; OPT: store i1 false
+; OPT: bb3:
+; OPT: store i1 false
+; OPT: store i1 false
+; OPT-NOT: add
+
+; LLC-LABEL: avalon
+; LLC-DAG: movs r{{[0-9]+}}, #0
+; LLC-DAG: movs r{{[0-9]+}}, #0
+; LLC-DAG: movs r{{[0-9]+}}, #1
+; LLC-NOT: add
+
+ at global = local_unnamed_addr global i1 undef, align 1
+ at global.0 = local_unnamed_addr global i1 undef, align 1
+
+define void @avalon() #0 {
+bb:
+ switch i8 undef, label %bb5 [
+ i8 0, label %bb1
+ i8 -1, label %bb2
+ i8 1, label %bb3
+ ]
+
+bb1:
+ store i1 1, i1* @global, align 1
+ unreachable
+
+bb2:
+ store i1 0, i1* @global, align 1
+ unreachable
+
+bb3:
+ store i1 0, i1* @global.0, align 1
+ store i1 0, i1* @global, align 1
+ unreachable
+
+bb5:
+ ret void
+}
+
+; Test that for i8 type, constant -1 is not rebased since it's the only
+; dependent of base constant -2.
+; This test is also covered by r342898, see
+; test/CodeGen/Thumb/consthoist-imm8-costs-1.ll
+
+; OPT-2-LABEL: barney
+; OPT-2: bb1:
+; OPT-2: store i8 -1
+; OPT-2: bb2:
+; OPT-2: store i8 -2
+; OPT-2: bb3:
+; OPT-2: store i8 -2
+; OPT-2: store i8 -2
+; OPT-2-NOT: add
+
+; LLC-LABEL: barney
+; LLC-DAG: movs r{{[0-9]+}}, #254
+; LLC-DAG: movs r{{[0-9]+}}, #255
+; LLC-NOT: mvn
+; LLC-NOT: add
+
+ at global.1 = local_unnamed_addr global i8 undef, align 1
+ at global.2 = local_unnamed_addr global i8 undef, align 1
+
+define void @barney() #0 {
+bb:
+ switch i8 undef, label %bb5 [
+ i8 0, label %bb1
+ i8 -1, label %bb2
+ i8 1, label %bb3
+ ]
+
+bb1: ; preds = %bb
+ store i8 -1, i8* @global.1, align 1
+ unreachable
+
+bb2: ; preds = %bb
+ store i8 -2, i8* @global.1, align 1
+ unreachable
+
+bb3: ; preds = %bb
+ store i8 -2, i8* @global.2, align 1
+ store i8 -2, i8* @global.1, align 1
+ unreachable
+
+bb5: ; preds = %bb
+ ret void
+}
+
+; Test that for i16 type constant 65532 is not rebased if it's the only
+; dependent of base constant 65531. Cost would be the same if rebased.
+; If rebased, 3 two-byte instructions:
+; movs r0, #4
+; mvns r0, r0
+; adds r0, r0, #1
+; If NOT rebased, 1 two-byte instruction plus 1 four-byte CP entry:
+; ldr r1, .LCPI2_3
+; ...
+; .LCPI2_3:
+; .long 65532
+
+; OPT-LABEL: carla
+
+; -consthoist-min-num-to-rebase=1, check that 65532 and single use of 65531
+; in bb2 is rebased
+; OPT-1: bb1:
+; OPT-1: %[[C1:const[0-9]?]] = bitcast i16 -5 to i16
+; OPT-1-NEXT: %const_mat = add i16 %[[C1]], 1
+; OPT-1-NEXT: store i16 %const_mat, i16* @global.3, align 1
+; OPT-1: bb2:
+; OPT-1-NEXT: %[[C2:const[0-9]?]] = bitcast i16 -5 to i16
+; OPT-1-NEXT: store i16 %[[C2]], i16* @global.3, align 1
+; OPT-1: bb3:
+; OPT-1-NEXT: %[[C3:const[0-9]?]] = bitcast i16 -5 to i16
+; OPT-1-NEXT: store i16 %[[C3]], i16* @global.4, align 1
+; OPT-1-NEXT: store i16 %[[C3]], i16* @global.3, align 1
+
+; -consthoist-min-num-to-rebase=2, check that 65532 and single use of 65531
+; in bb2 is not rebased
+; OPT-2: bb1:
+; OPT-2-NEXT: store i16 -4, i16* @global.3, align 1
+; OPT-2: bb2:
+; OPT-2-NEXT: store i16 -5, i16* @global.3, align 1
+; OPT-2: bb3:
+; OPT-2-NEXT: %[[C4:const[0-9]?]] = bitcast i16 -5 to i16
+; OPT-2-NEXT: store i16 %[[C4]], i16* @global.4, align 1
+; OPT-2-NEXT: store i16 %[[C4]], i16* @global.3, align 1
+; OPT-2-NOT: add
+
+; -consthoist-min-num-to-rebase=3, check that dual uses of 65531 in bb3 are
+; not rebase
+; OPT-3: bb1:
+; OPT-3-NEXT: store i16 -4, i16* @global.3, align 1
+; OPT-3: bb2:
+; OPT-3-NEXT: store i16 -5, i16* @global.3, align 1
+; OPT-3: bb3:
+; OPT-3-NEXT: store i16 -5, i16* @global.4, align 1
+; OPT-3-NEXT: store i16 -5, i16* @global.3, align 1
+; OPT-3-NOT: add
+; OPT-3-NOT: bitcast
+
+; LLC-LABEL: carla
+; LLC-DAG: ldr r{{[0-9]+}}, .LCPI2_1
+; LLC-DAG: ldr r{{[0-9]+}}, .LCPI2_3
+; LLC-NOT: mvn
+; LLC-NOT: add
+
+ at global.3 = local_unnamed_addr global i16 undef, align 2
+ at global.4 = local_unnamed_addr global i16 undef, align 2
+
+define void @carla() {
+bb:
+ switch i8 undef, label %bb5 [
+ i8 0, label %bb1
+ i8 -1, label %bb2
+ i8 1, label %bb3
+ ]
+
+bb1: ; preds = %bb
+ store i16 65532, i16* @global.3, align 1
+ unreachable
+
+bb2: ; preds = %bb
+ store i16 65531, i16* @global.3, align 1
+ unreachable
+
+bb3: ; preds = %bb
+ store i16 65531, i16* @global.4, align 1
+ store i16 65531, i16* @global.3, align 1
+ unreachable
+
+bb5: ; preds = %bb
+ ret void
+}
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