[LLVMbugs] [Bug 1768] New: correlatedexpression optimization needs 2 passes, and misses optimization due to function parameter order

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=1768

           Summary: correlatedexpression optimization needs 2 passes, and
                    misses optimization due to function parameter order
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: minor
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: edwintorok at gmail.com
                CC: llvmbugs at cs.uiuc.edu


Consider these 2 functions opt_fail and opt_ok, where only the order of the
parameters is different.
In opt_fail's case llvm doesn't recognize the optimization opportunity in
cond_true, while it recognizes it in opt_ok.
Also it takes an additional run of opt to actually optimize out the sub
instruction in opt_ok.

I think opt should optimize out the sub in one pass for opt_ok.
For opt_fail: if i==j, it should recognize that j==i too (unless this would
cause infinite loops).

; ModuleID = 'foo.bc'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"

define i32 @opt_fail(i32 %i, i32 %j) {
entry:
        %tmp7 = icmp eq i32 %i, %j              ; <i1> [#uses=1]
        br i1 %tmp7, label %cond_true, label %UnifiedReturnBlock1

cond_true:              ; preds = %entry
        %tmp11 = sub i32 %i, %j         ; <i32> [#uses=1]
        ret i32 %tmp11

UnifiedReturnBlock1:            ; preds = %entry
        ret i32 5
}

define i32 @opt_ok(i32 %j, i32 %i) {
entry:
        %tmp7 = icmp eq i32 %i, %j              ; <i1> [#uses=1]
        br i1 %tmp7, label %cond_true, label %UnifiedReturnBlock1

cond_true:              ; preds = %entry
        %tmp11 = sub i32 %i, %j         ; <i32> [#uses=1]
        ret i32 %tmp11

UnifiedReturnBlock1:            ; preds = %entry
        ret i32 5
}




$ opt -cee -std-compile-opts -debug-only=cee foo.bc -o foo2.bc -f
 RegionInfo for basic block: cond_true
  ValueInfo for: i32 %i
    Bounds = [-1,-1 )
    is == i32 %j
  ValueInfo for: i32 %j
    Bounds = [-1,-1 )
    is == i32 %j
  ValueInfo for: i1 %tmp7
    Bounds = [-1,0 )
    Replacement = i1 true
    is == i1 true

 RegionInfo for basic block: UnifiedReturnBlock
  ValueInfo for: i32 %i
    Bounds = [-1,-1 )
    is != i32 %j
  ValueInfo for: i32 %j
    Bounds = [-1,-1 )
    is != i32 %i
  ValueInfo for: i1 %tmp7
    Bounds = [0,-1 )
    Replacement = i1 false
    is == i1 false

 RegionInfo for basic block: cond_true
  ValueInfo for: i1 %tmp7
    Bounds = [-1,0 )
    Replacement = i1 true
    is == i1 true
  ValueInfo for: i32 %j
    Bounds = [-1,-1 )
    is == i32 %j
  ValueInfo for: i32 %i
    Bounds = [-1,-1 )
    Replacement = i32 %j
    is == i32 %j

In Inst:        %tmp11 = sub i32 %i, %j         ; <i32> [#uses=1]
  Replacing operand #0 with i32 %j
 RegionInfo for basic block: UnifiedReturnBlock
  ValueInfo for: i1 %tmp7
    Bounds = [0,-1 )
    Replacement = i1 false
    is == i1 false
  ValueInfo for: i32 %j
    Bounds = [-1,-1 )
    is != i32 %i
  ValueInfo for: i32 %i
    Bounds = [-1,-1 )
    is != i32 %j


; ModuleID = 'foo2.bc'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"

define i32 @opt_fail(i32 %i, i32 %j) {
entry:
        %tmp7 = icmp eq i32 %i, %j              ; <i1> [#uses=1]
        br i1 %tmp7, label %cond_true, label %UnifiedReturnBlock

cond_true:              ; preds = %entry
        %tmp11 = sub i32 %i, %j         ; <i32> [#uses=1]
        ret i32 %tmp11

UnifiedReturnBlock:             ; preds = %entry
        ret i32 5
}

define i32 @opt_ok(i32 %j, i32 %i) {
entry:
        %tmp7 = icmp eq i32 %i, %j              ; <i1> [#uses=1]
        br i1 %tmp7, label %cond_true, label %UnifiedReturnBlock

cond_true:              ; preds = %entry
        %tmp11 = sub i32 %j, %j         ; <i32> [#uses=1]
        ret i32 %tmp11

UnifiedReturnBlock:             ; preds = %entry
        ret i32 5
}


$ opt -std-compile-opts foo2.bc -o foo3.bc -f
 ModuleID = 'foo3.bc'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"

define i32 @opt_fail(i32 %i, i32 %j) {
entry:
        %tmp7 = icmp eq i32 %i, %j              ; <i1> [#uses=1]
        br i1 %tmp7, label %cond_true, label %UnifiedReturnBlock1

cond_true:              ; preds = %entry
        %tmp11 = sub i32 %i, %j         ; <i32> [#uses=1]
        ret i32 %tmp11

UnifiedReturnBlock1:            ; preds = %entry
        ret i32 5
}

define i32 @opt_ok(i32 %j, i32 %i) {
entry:
        %tmp7 = icmp eq i32 %i, %j              ; <i1> [#uses=1]
        %retval = select i1 %tmp7, i32 0, i32 5         ; <i32> [#uses=1]
        ret i32 %retval
}


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