[llvm] 787dba7 - [LICM] Hoisting of widenable conditions out of loops
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Fri Nov 8 08:19:54 PST 2019
Author: Philip Reames
Date: 2019-11-08T08:19:48-08:00
New Revision: 787dba7aae1d01f3fcf1e471f733f00a6ba66e33
URL: https://github.com/llvm/llvm-project/commit/787dba7aae1d01f3fcf1e471f733f00a6ba66e33
DIFF: https://github.com/llvm/llvm-project/commit/787dba7aae1d01f3fcf1e471f733f00a6ba66e33.diff
LOG: [LICM] Hoisting of widenable conditions out of loops
The change itself is straight forward and obvious, but ... there's an existing test checking for exactly the opposite. Both I and Artur think this is simply conservatism in the initial implementation. If anyone bisects a problem to this, a counter example will be very interesting.
Differential Revision: https://reviews.llvm.org/D69907
Added:
Modified:
llvm/include/llvm/IR/Intrinsics.td
llvm/lib/Transforms/Scalar/LICM.cpp
llvm/test/Transforms/LICM/explicit_guards.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
index 7a0263f88c2a..cc29a9c9bbcb 100644
--- a/llvm/include/llvm/IR/Intrinsics.td
+++ b/llvm/include/llvm/IR/Intrinsics.td
@@ -1070,7 +1070,7 @@ def int_experimental_guard : Intrinsic<[], [llvm_i1_ty, llvm_vararg_ty],
// Supports widenable conditions for guards represented as explicit branches.
def int_experimental_widenable_condition : Intrinsic<[llvm_i1_ty], [],
- [IntrInaccessibleMemOnly, IntrWillReturn]>;
+ [IntrInaccessibleMemOnly, IntrWillReturn, IntrSpeculatable]>;
// NOP: calls/invokes to this intrinsic are removed by codegen
def int_donothing : Intrinsic<[], [], [IntrNoMem, IntrWillReturn]>;
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 70868ed8c187..c239edaf6667 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -1144,6 +1144,10 @@ bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
// Assumes don't actually alias anything or throw
return true;
+ if (match(CI, m_Intrinsic<Intrinsic::experimental_widenable_condition>()))
+ // Widenable conditions don't actually alias anything or throw
+ return true;
+
// Handle simple cases by querying alias analysis.
FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI);
if (Behavior == FMRB_DoesNotAccessMemory)
diff --git a/llvm/test/Transforms/LICM/explicit_guards.ll b/llvm/test/Transforms/LICM/explicit_guards.ll
index c9e091359b0a..a684ebe9d88a 100644
--- a/llvm/test/Transforms/LICM/explicit_guards.ll
+++ b/llvm/test/Transforms/LICM/explicit_guards.ll
@@ -2,21 +2,54 @@
; RUN: opt -S -make-guards-explicit -basicaa -licm < %s | FileCheck %s
; RUN: opt -S -aa-pipeline=basic-aa -passes='require<opt-remark-emit>,make-guards-explicit,loop(licm)' < %s | FileCheck %s
-; Test interaction between explicit guards and LICM: make sure that we do not
-; hoist explicit conditions while we can hoist invariant loads in presence of
-; explicit guards.
-
declare void @llvm.experimental.guard(i1,...)
+declare void @maythrow()
; Make sure that we do not hoist widenable_cond out of loop.
-define void @do_not_hoist_widenable_cond(i1 %cond, i32 %N, i32 %M) {
-; CHECK-LABEL: @do_not_hoist_widenable_cond(
+define void @hoist_widenable_cond(i1 %cond, i32 %N, i32 %M) {
+; CHECK-LABEL: @hoist_widenable_cond(
; CHECK-NEXT: entry:
+; CHECK-NEXT: [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[GUARDED:%.*]] ]
; CHECK-NEXT: [[GUARD_COND:%.*]] = icmp slt i32 [[IV]], [[N:%.*]]
+; CHECK-NEXT: [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[GUARD_COND]], [[WIDENABLE_COND]]
+; CHECK-NEXT: br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK: deopt:
+; CHECK-NEXT: call void (...) @llvm.experimental.deoptimize.isVoid() [ "deopt"() ]
+; CHECK-NEXT: ret void
+; CHECK: guarded:
+; CHECK-NEXT: [[LOOP_COND:%.*]] = icmp slt i32 [[IV]], [[M:%.*]]
+; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
+; CHECK-NEXT: br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK: exit:
+; CHECK-NEXT: ret void
+;
+entry:
+ br label %loop
+
+loop:
+ %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
+ %guard_cond = icmp slt i32 %iv, %N
+ call void(i1, ...) @llvm.experimental.guard(i1 %guard_cond) [ "deopt"() ]
+ %loop_cond = icmp slt i32 %iv, %M
+ %iv.next = add i32 %iv, 1
+ br i1 %loop_cond, label %loop, label %exit
+
+exit:
+ ret void
+}
+
+define void @hoist_widenable_cond_speculate(i1 %cond, i32 %N, i32 %M) {
+; CHECK-LABEL: @hoist_widenable_cond_speculate(
+; CHECK-NEXT: entry:
; CHECK-NEXT: [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[GUARDED:%.*]] ]
+; CHECK-NEXT: [[GUARD_COND:%.*]] = icmp slt i32 [[IV]], [[N:%.*]]
+; CHECK-NEXT: call void @maythrow()
; CHECK-NEXT: [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[GUARD_COND]], [[WIDENABLE_COND]]
; CHECK-NEXT: br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
; CHECK: deopt:
@@ -35,6 +68,7 @@ entry:
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
%guard_cond = icmp slt i32 %iv, %N
+ call void @maythrow()
call void(i1, ...) @llvm.experimental.guard(i1 %guard_cond) [ "deopt"() ]
%loop_cond = icmp slt i32 %iv, %M
%iv.next = add i32 %iv, 1
@@ -44,15 +78,16 @@ exit:
ret void
}
+
define void @hoist_invariant_load(i1 %cond, i32* %np, i32 %M) {
; CHECK-LABEL: @hoist_invariant_load(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N:%.*]] = load i32, i32* [[NP:%.*]]
+; CHECK-NEXT: [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[GUARDED:%.*]] ]
; CHECK-NEXT: [[GUARD_COND:%.*]] = icmp slt i32 [[IV]], [[N]]
-; CHECK-NEXT: [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
; CHECK-NEXT: [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[GUARD_COND]], [[WIDENABLE_COND]]
; CHECK-NEXT: br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
; CHECK: deopt:
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