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clang-p2996/llvm/test/Transforms/LoopUnroll/2011-08-08-PhiUpdate.ll
Philip Reames de2fed6152 [unroll] Keep unrolled iterations with initial iteration 
The unrolling code was previously inserting new cloned blocks at the end of the function.  The result of this with typical loop structures is that the new iterations are placed far from the initial iteration.

With unrolling, the general assumption is that the a) the loop is reasonable hot, and b) the first Count-1 copies of the loop are rarely (if ever) loop exiting.  As such, placing Count-1 copies out of line is a fairly poor code placement choice.  We'd much rather fall through into the hot (non-exiting) path.  For code with branch profiles, later layout would fix this, but this may have a positive impact on non-PGO compiled code.

However, the real motivation for this change isn't performance.  Its readability and human understanding.  Having to jump around long distances in an IR file to trace an unrolled loop structure is error prone and tedious.
2021-11-12 11:40:50 -08:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -loop-unroll -S -unroll-count=4 | FileCheck %s
; Test phi update after partial unroll.
declare i1 @check() nounwind
define void @test1(i32 %i, i32 %j) nounwind uwtable ssp {
;
; CHECK-LABEL: @test1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[COND1:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND1]], label [[IF_THEN:%.*]], label [[IF_ELSE_LR_PH:%.*]]
; CHECK: if.else.lr.ph:
; CHECK-NEXT: br label [[IF_ELSE:%.*]]
; CHECK: if.else:
; CHECK-NEXT: [[SUB:%.*]] = phi i32 [ [[I:%.*]], [[IF_ELSE_LR_PH]] ], [ [[SUB5_3:%.*]], [[IF_ELSE_3:%.*]] ]
; CHECK-NEXT: [[SUB5:%.*]] = sub i32 [[SUB]], [[J:%.*]]
; CHECK-NEXT: [[COND2:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2]], label [[IF_THEN_LOOPEXIT:%.*]], label [[IF_ELSE_1:%.*]]
; CHECK: if.else.1:
; CHECK-NEXT: [[SUB5_1:%.*]] = sub i32 [[SUB5]], [[J]]
; CHECK-NEXT: [[COND2_1:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2_1]], label [[IF_THEN_LOOPEXIT]], label [[IF_ELSE_2:%.*]]
; CHECK: if.else.2:
; CHECK-NEXT: [[SUB5_2:%.*]] = sub i32 [[SUB5_1]], [[J]]
; CHECK-NEXT: [[COND2_2:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2_2]], label [[IF_THEN_LOOPEXIT]], label [[IF_ELSE_3]]
; CHECK: if.else.3:
; CHECK-NEXT: [[SUB5_3]] = sub i32 [[SUB5_2]], [[J]]
; CHECK-NEXT: [[COND2_3:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2_3]], label [[IF_THEN_LOOPEXIT]], label [[IF_ELSE]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: if.then.loopexit:
; CHECK-NEXT: [[SUB5_LCSSA:%.*]] = phi i32 [ [[SUB5]], [[IF_ELSE]] ], [ [[SUB5_1]], [[IF_ELSE_1]] ], [ [[SUB5_2]], [[IF_ELSE_2]] ], [ [[SUB5_3]], [[IF_ELSE_3]] ]
; CHECK-NEXT: br label [[IF_THEN]]
; CHECK: if.then:
; CHECK-NEXT: [[I_TR:%.*]] = phi i32 [ [[I]], [[ENTRY:%.*]] ], [ [[SUB5_LCSSA]], [[IF_THEN_LOOPEXIT]] ]
; CHECK-NEXT: ret void
;
entry:
%cond1 = call zeroext i1 @check()
br i1 %cond1, label %if.then, label %if.else.lr.ph
if.else.lr.ph: ; preds = %entry
br label %if.else
if.else: ; preds = %if.else, %if.else.lr.ph
%sub = phi i32 [ %i, %if.else.lr.ph ], [ %sub5, %if.else ]
%sub5 = sub i32 %sub, %j
%cond2 = call zeroext i1 @check()
br i1 %cond2, label %if.then, label %if.else
if.then: ; preds = %if.else, %entry
%i.tr = phi i32 [ %i, %entry ], [ %sub5, %if.else ]
ret void
}
; PR7318: assertion failure after doing a simple loop unroll
;
define i32 @test2(i32* nocapture %p, i32 %n) nounwind readonly {
;
; CHECK-LABEL: @test2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = icmp sgt i32 [[N:%.*]], 0
; CHECK-NEXT: br i1 [[TMP0]], label [[BB_NPH:%.*]], label [[BB2:%.*]]
; CHECK: bb.nph:
; CHECK-NEXT: [[TMP:%.*]] = zext i32 [[N]] to i64
; CHECK-NEXT: br label [[BB:%.*]]
; CHECK: bb:
; CHECK-NEXT: [[INDVAR:%.*]] = phi i64 [ 0, [[BB_NPH]] ], [ [[INDVAR_NEXT_3:%.*]], [[BB1_3:%.*]] ]
; CHECK-NEXT: [[S_01:%.*]] = phi i32 [ 0, [[BB_NPH]] ], [ [[TMP8:%.*]], [[BB1_3]] ]
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i32, i32* [[P:%.*]], i64 [[INDVAR]]
; CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* [[SCEVGEP]], align 1
; CHECK-NEXT: [[TMP2:%.*]] = add nsw i32 [[TMP1]], [[S_01]]
; CHECK-NEXT: br label [[BB1:%.*]]
; CHECK: bb1:
; CHECK-NEXT: [[INDVAR_NEXT:%.*]] = add nuw nsw i64 [[INDVAR]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i64 [[INDVAR_NEXT]], [[TMP]]
; CHECK-NEXT: br i1 [[EXITCOND]], label [[BB_1:%.*]], label [[BB1_BB2_CRIT_EDGE:%.*]]
; CHECK: bb.1:
; CHECK-NEXT: [[SCEVGEP_1:%.*]] = getelementptr i32, i32* [[P]], i64 [[INDVAR_NEXT]]
; CHECK-NEXT: [[TMP3:%.*]] = load i32, i32* [[SCEVGEP_1]], align 1
; CHECK-NEXT: [[TMP4:%.*]] = add nsw i32 [[TMP3]], [[TMP2]]
; CHECK-NEXT: br label [[BB1_1:%.*]]
; CHECK: bb1.1:
; CHECK-NEXT: [[INDVAR_NEXT_1:%.*]] = add nuw nsw i64 [[INDVAR_NEXT]], 1
; CHECK-NEXT: [[EXITCOND_1:%.*]] = icmp ne i64 [[INDVAR_NEXT_1]], [[TMP]]
; CHECK-NEXT: br i1 [[EXITCOND_1]], label [[BB_2:%.*]], label [[BB1_BB2_CRIT_EDGE]]
; CHECK: bb.2:
; CHECK-NEXT: [[SCEVGEP_2:%.*]] = getelementptr i32, i32* [[P]], i64 [[INDVAR_NEXT_1]]
; CHECK-NEXT: [[TMP5:%.*]] = load i32, i32* [[SCEVGEP_2]], align 1
; CHECK-NEXT: [[TMP6:%.*]] = add nsw i32 [[TMP5]], [[TMP4]]
; CHECK-NEXT: br label [[BB1_2:%.*]]
; CHECK: bb1.2:
; CHECK-NEXT: [[INDVAR_NEXT_2:%.*]] = add nuw nsw i64 [[INDVAR_NEXT_1]], 1
; CHECK-NEXT: [[EXITCOND_2:%.*]] = icmp ne i64 [[INDVAR_NEXT_2]], [[TMP]]
; CHECK-NEXT: br i1 [[EXITCOND_2]], label [[BB_3:%.*]], label [[BB1_BB2_CRIT_EDGE]]
; CHECK: bb.3:
; CHECK-NEXT: [[SCEVGEP_3:%.*]] = getelementptr i32, i32* [[P]], i64 [[INDVAR_NEXT_2]]
; CHECK-NEXT: [[TMP7:%.*]] = load i32, i32* [[SCEVGEP_3]], align 1
; CHECK-NEXT: [[TMP8]] = add nsw i32 [[TMP7]], [[TMP6]]
; CHECK-NEXT: br label [[BB1_3]]
; CHECK: bb1.3:
; CHECK-NEXT: [[INDVAR_NEXT_3]] = add i64 [[INDVAR_NEXT_2]], 1
; CHECK-NEXT: [[EXITCOND_3:%.*]] = icmp ne i64 [[INDVAR_NEXT_3]], [[TMP]]
; CHECK-NEXT: br i1 [[EXITCOND_3]], label [[BB]], label [[BB1_BB2_CRIT_EDGE]], !llvm.loop [[LOOP2:![0-9]+]]
; CHECK: bb1.bb2_crit_edge:
; CHECK-NEXT: [[DOTLCSSA:%.*]] = phi i32 [ [[TMP2]], [[BB1]] ], [ [[TMP4]], [[BB1_1]] ], [ [[TMP6]], [[BB1_2]] ], [ [[TMP8]], [[BB1_3]] ]
; CHECK-NEXT: br label [[BB2]]
; CHECK: bb2:
; CHECK-NEXT: [[S_0_LCSSA:%.*]] = phi i32 [ [[DOTLCSSA]], [[BB1_BB2_CRIT_EDGE]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i32 [[S_0_LCSSA]]
;
entry:
%0 = icmp sgt i32 %n, 0 ; <i1> [#uses=1]
br i1 %0, label %bb.nph, label %bb2
bb.nph: ; preds = %entry
%tmp = zext i32 %n to i64 ; <i64> [#uses=1]
br label %bb
bb: ; preds = %bb.nph, %bb1
%indvar = phi i64 [ 0, %bb.nph ], [ %indvar.next, %bb1 ] ; <i64> [#uses=2]
%s.01 = phi i32 [ 0, %bb.nph ], [ %2, %bb1 ] ; <i32> [#uses=1]
%scevgep = getelementptr i32, i32* %p, i64 %indvar ; <i32*> [#uses=1]
%1 = load i32, i32* %scevgep, align 1 ; <i32> [#uses=1]
%2 = add nsw i32 %1, %s.01 ; <i32> [#uses=2]
br label %bb1
bb1: ; preds = %bb
%indvar.next = add i64 %indvar, 1 ; <i64> [#uses=2]
%exitcond = icmp ne i64 %indvar.next, %tmp ; <i1> [#uses=1]
br i1 %exitcond, label %bb, label %bb1.bb2_crit_edge
bb1.bb2_crit_edge: ; preds = %bb1
%.lcssa = phi i32 [ %2, %bb1 ] ; <i32> [#uses=1]
br label %bb2
bb2: ; preds = %bb1.bb2_crit_edge, %entry
%s.0.lcssa = phi i32 [ %.lcssa, %bb1.bb2_crit_edge ], [ 0, %entry ] ; <i32> [#uses=1]
ret i32 %s.0.lcssa
}
; Check phi update for loop with an early-exit.
;
define i32 @test3() nounwind uwtable ssp align 2 {
;
; CHECK-LABEL: @test3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[COND1:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND1]], label [[RETURN:%.*]], label [[IF_END:%.*]]
; CHECK: if.end:
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[COND2:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2]], label [[EXIT:%.*]], label [[DO_COND:%.*]]
; CHECK: exit:
; CHECK-NEXT: [[TMP7_I:%.*]] = load i32, i32* undef, align 8
; CHECK-NEXT: br i1 undef, label [[DO_COND]], label [[LAND_LHS_TRUE:%.*]]
; CHECK: land.lhs.true:
; CHECK-NEXT: br i1 true, label [[RETURN_LOOPEXIT:%.*]], label [[DO_COND]]
; CHECK: do.cond:
; CHECK-NEXT: [[COND3:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND3]], label [[DO_END:%.*]], label [[DO_BODY_1:%.*]]
; CHECK: do.body.1:
; CHECK-NEXT: [[COND2_1:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2_1]], label [[EXIT_1:%.*]], label [[DO_COND_1:%.*]]
; CHECK: exit.1:
; CHECK-NEXT: [[TMP7_I_1:%.*]] = load i32, i32* undef, align 8
; CHECK-NEXT: br i1 undef, label [[DO_COND_1]], label [[LAND_LHS_TRUE_1:%.*]]
; CHECK: land.lhs.true.1:
; CHECK-NEXT: br i1 true, label [[RETURN_LOOPEXIT]], label [[DO_COND_1]]
; CHECK: do.cond.1:
; CHECK-NEXT: [[COND3_1:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND3_1]], label [[DO_END]], label [[DO_BODY_2:%.*]]
; CHECK: do.body.2:
; CHECK-NEXT: [[COND2_2:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2_2]], label [[EXIT_2:%.*]], label [[DO_COND_2:%.*]]
; CHECK: exit.2:
; CHECK-NEXT: [[TMP7_I_2:%.*]] = load i32, i32* undef, align 8
; CHECK-NEXT: br i1 undef, label [[DO_COND_2]], label [[LAND_LHS_TRUE_2:%.*]]
; CHECK: land.lhs.true.2:
; CHECK-NEXT: br i1 true, label [[RETURN_LOOPEXIT]], label [[DO_COND_2]]
; CHECK: do.cond.2:
; CHECK-NEXT: [[COND3_2:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND3_2]], label [[DO_END]], label [[DO_BODY_3:%.*]]
; CHECK: do.body.3:
; CHECK-NEXT: [[COND2_3:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND2_3]], label [[EXIT_3:%.*]], label [[DO_COND_3:%.*]]
; CHECK: exit.3:
; CHECK-NEXT: [[TMP7_I_3:%.*]] = load i32, i32* undef, align 8
; CHECK-NEXT: br i1 undef, label [[DO_COND_3]], label [[LAND_LHS_TRUE_3:%.*]]
; CHECK: land.lhs.true.3:
; CHECK-NEXT: br i1 true, label [[RETURN_LOOPEXIT]], label [[DO_COND_3]]
; CHECK: do.cond.3:
; CHECK-NEXT: [[COND3_3:%.*]] = call zeroext i1 @check()
; CHECK-NEXT: br i1 [[COND3_3]], label [[DO_END]], label [[DO_BODY]], !llvm.loop [[LOOP3:![0-9]+]]
; CHECK: do.end:
; CHECK-NEXT: br label [[RETURN]]
; CHECK: return.loopexit:
; CHECK-NEXT: [[TMP7_I_LCSSA:%.*]] = phi i32 [ [[TMP7_I]], [[LAND_LHS_TRUE]] ], [ [[TMP7_I_1]], [[LAND_LHS_TRUE_1]] ], [ [[TMP7_I_2]], [[LAND_LHS_TRUE_2]] ], [ [[TMP7_I_3]], [[LAND_LHS_TRUE_3]] ]
; CHECK-NEXT: br label [[RETURN]]
; CHECK: return:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ 0, [[DO_END]] ], [ 0, [[ENTRY:%.*]] ], [ [[TMP7_I_LCSSA]], [[RETURN_LOOPEXIT]] ]
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
entry:
%cond1 = call zeroext i1 @check()
br i1 %cond1, label %return, label %if.end
if.end: ; preds = %entry
br label %do.body
do.body: ; preds = %do.cond, %if.end
%cond2 = call zeroext i1 @check()
br i1 %cond2, label %exit, label %do.cond
exit: ; preds = %do.body
%tmp7.i = load i32, i32* undef, align 8
br i1 undef, label %do.cond, label %land.lhs.true
land.lhs.true: ; preds = %exit
br i1 undef, label %return, label %do.cond
do.cond: ; preds = %land.lhs.true, %exit, %do.body
%cond3 = call zeroext i1 @check()
br i1 %cond3, label %do.end, label %do.body
do.end: ; preds = %do.cond
br label %return
return: ; preds = %do.end, %land.lhs.true, %entry
%retval.0 = phi i32 [ 0, %do.end ], [ 0, %entry ], [ %tmp7.i, %land.lhs.true ]
ret i32 %retval.0
}
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