llvm/test/CodeGen/ARM/ifcvt4.ll
Cong Hou 759d988de3 Scaling up values in ARMBaseInstrInfo::isProfitableToIfCvt() before they are scaled by a probability to avoid precision issue.
In ARMBaseInstrInfo::isProfitableToIfCvt(), there is a simple cost model in which the number of cycles is scaled by a probability to estimate the cost. However, when the number of cycles is small (which is usually the case), there is a precision issue after the computation. To avoid this issue, this patch scales those cycles by 1024 (chosen to make the multiplication a litter faster) before they are scaled by the probability. Other variables are also scaled up for the final comparison.

Differential Revision: http://reviews.llvm.org/D12742



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248018 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-18 18:19:40 +00:00

39 lines
1.5 KiB
LLVM

; RUN: llc -mtriple=arm-eabi %s -o - | FileCheck %s
; CHECK-LABEL: t:
; CHECK: subgt
; CHECK: suble
define i32 @t(i32 %a, i32 %b) {
entry:
%tmp1434 = icmp eq i32 %a, %b ; <i1> [#uses=1]
br i1 %tmp1434, label %bb17, label %bb.outer
bb.outer: ; preds = %cond_false, %entry
%b_addr.021.0.ph = phi i32 [ %b, %entry ], [ %tmp10, %cond_false ] ; <i32> [#uses=5]
%a_addr.026.0.ph = phi i32 [ %a, %entry ], [ %a_addr.026.0, %cond_false ] ; <i32> [#uses=1]
br label %bb
bb: ; preds = %cond_true, %bb.outer
%indvar = phi i32 [ 0, %bb.outer ], [ %indvar.next, %cond_true ] ; <i32> [#uses=2]
%tmp. = sub i32 0, %b_addr.021.0.ph ; <i32> [#uses=1]
%tmp.40 = mul i32 %indvar, %tmp. ; <i32> [#uses=1]
%a_addr.026.0 = add i32 %tmp.40, %a_addr.026.0.ph ; <i32> [#uses=6]
%tmp3 = icmp sgt i32 %a_addr.026.0, %b_addr.021.0.ph ; <i1> [#uses=1]
br i1 %tmp3, label %cond_true, label %cond_false
cond_true: ; preds = %bb
%tmp7 = sub i32 %a_addr.026.0, %b_addr.021.0.ph ; <i32> [#uses=2]
%tmp1437 = icmp eq i32 %tmp7, %b_addr.021.0.ph ; <i1> [#uses=1]
%indvar.next = add i32 %indvar, 1 ; <i32> [#uses=1]
br i1 %tmp1437, label %bb17, label %bb
cond_false: ; preds = %bb
%tmp10 = sub i32 %b_addr.021.0.ph, %a_addr.026.0 ; <i32> [#uses=2]
%tmp14 = icmp eq i32 %a_addr.026.0, %tmp10 ; <i1> [#uses=1]
br i1 %tmp14, label %bb17, label %bb.outer
bb17: ; preds = %cond_false, %cond_true, %entry
%a_addr.026.1 = phi i32 [ %a, %entry ], [ %tmp7, %cond_true ], [ %a_addr.026.0, %cond_false ] ; <i32> [#uses=1]
ret i32 %a_addr.026.1
}