cmd/compile: improve testing of induction variables

Test both minimum and maximum bound, and prepare
formatting for more advanced tests (inclusive / esclusive bounds).

Change-Id: Ibe432916d9c938343bc07943798bc9709ad71845
Reviewed-on: https://go-review.googlesource.com/104040
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/ssa/loopbce.go

 package ssa
 
+import "fmt"
+
 type indVar struct {
 	ind   *Value // induction variable
 	inc   *Value // increment, a constant
@@ -138,11 +140,22 @@ nextb:
 		}
 
 		if f.pass.debug >= 1 {
-			if min.Op == OpConst64 {
-				b.Func.Warnl(b.Pos, "Induction variable with minimum %d and increment %d", min.AuxInt, inc.AuxInt)
+			mlim1, mlim2 := fmt.Sprint(min.AuxInt), fmt.Sprint(max.AuxInt)
+			if !min.isGenericIntConst() {
+				if f.pass.debug >= 2 {
+					mlim1 = fmt.Sprint(min)
 				} else {
-				b.Func.Warnl(b.Pos, "Induction variable with non-const minimum and increment %d", inc.AuxInt)
+					mlim1 = "?"
+				}
+			}
+			if !max.isGenericIntConst() {
+				if f.pass.debug >= 2 {
+					mlim2 = fmt.Sprint(max)
+				} else {
+					mlim2 = "?"
+				}
 			}
+			b.Func.Warnl(b.Pos, "Induction variable: limits [%v,%v), increment %d", mlim1, mlim2, inc.AuxInt)
 		}
 
 		iv = append(iv, indVar{

test/loopbce.go

@@ -5,7 +5,7 @@ package main
 
 func f0a(a []int) int {
 	x := 0
-	for i := range a { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		x += a[i] // ERROR "Proved IsInBounds$"
 	}
 	return x
@@ -13,7 +13,7 @@ func f0a(a []int) int {
 
 func f0b(a []int) int {
 	x := 0
-	for i := range a { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		b := a[i:] // ERROR "Proved IsSliceInBounds$"
 		x += b[0]
 	}
@@ -22,7 +22,7 @@ func f0b(a []int) int {
 
 func f0c(a []int) int {
 	x := 0
-	for i := range a { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		b := a[:i+1] // ERROR "Proved IsSliceInBounds$"
 		x += b[0]
 	}
@@ -31,7 +31,7 @@ func f0c(a []int) int {
 
 func f1(a []int) int {
 	x := 0
-	for _, i := range a { // ERROR "Induction variable with minimum 0 and increment 1"
+	for _, i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		x += i
 	}
 	return x
@@ -39,7 +39,7 @@ func f1(a []int) int {
 
 func f2(a []int) int {
 	x := 0
-	for i := 1; i < len(a); i++ { // ERROR "Induction variable with minimum 1 and increment 1$"
+	for i := 1; i < len(a); i++ { // ERROR "Induction variable: limits \[1,\?\), increment 1$"
 		x += a[i] // ERROR "Proved IsInBounds$"
 	}
 	return x
@@ -47,7 +47,7 @@ func f2(a []int) int {
 
 func f4(a [10]int) int {
 	x := 0
-	for i := 0; i < len(a); i += 2 { // ERROR "Induction variable with minimum 0 and increment 2$"
+	for i := 0; i < len(a); i += 2 { // ERROR "Induction variable: limits \[0,10\), increment 2$"
 		x += a[i] // ERROR "Proved IsInBounds$"
 	}
 	return x
@@ -55,14 +55,14 @@ func f4(a [10]int) int {
 
 func f5(a [10]int) int {
 	x := 0
-	for i := -10; i < len(a); i += 2 { // ERROR "Induction variable with minimum -10 and increment 2$"
+	for i := -10; i < len(a); i += 2 { // ERROR "Induction variable: limits \[-10,10\), increment 2$"
 		x += a[i]
 	}
 	return x
 }
 
 func f6(a []int) {
-	for i := range a { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		b := a[0:i] // ERROR "Proved IsSliceInBounds$"
 		f6(b)
 	}
@@ -70,7 +70,7 @@ func f6(a []int) {
 
 func g0a(a string) int {
 	x := 0
-	for i := 0; i < len(a); i++ { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := 0; i < len(a); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		x += int(a[i]) // ERROR "Proved IsInBounds$"
 	}
 	return x
@@ -78,7 +78,7 @@ func g0a(a string) int {
 
 func g0b(a string) int {
 	x := 0
-	for i := 0; len(a) > i; i++ { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := 0; len(a) > i; i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		x += int(a[i]) // ERROR "Proved IsInBounds$"
 	}
 	return x
@@ -87,7 +87,7 @@ func g0b(a string) int {
 func g1() int {
 	a := "evenlength"
 	x := 0
-	for i := 0; i < len(a); i += 2 { // ERROR "Induction variable with minimum 0 and increment 2$"
+	for i := 0; i < len(a); i += 2 { // ERROR "Induction variable: limits \[0,10\), increment 2$"
 		x += int(a[i]) // ERROR "Proved IsInBounds$"
 	}
 	return x
@@ -96,7 +96,7 @@ func g1() int {
 func g2() int {
 	a := "evenlength"
 	x := 0
-	for i := 0; i < len(a); i += 2 { // ERROR "Induction variable with minimum 0 and increment 2$"
+	for i := 0; i < len(a); i += 2 { // ERROR "Induction variable: limits \[0,10\), increment 2$"
 		j := i
 		if a[i] == 'e' { // ERROR "Proved IsInBounds$"
 			j = j + 1
@@ -108,39 +108,39 @@ func g2() int {
 
 func g3a() {
 	a := "this string has length 25"
-	for i := 0; i < len(a); i += 5 { // ERROR "Induction variable with minimum 0 and increment 5$"
+	for i := 0; i < len(a); i += 5 { // ERROR "Induction variable: limits \[0,25\), increment 5$"
 		useString(a[i:]) // ERROR "Proved IsSliceInBounds$"
 		useString(a[:i+3])
 	}
 }
 
 func g3b(a string) {
-	for i := 0; i < len(a); i++ { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := 0; i < len(a); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		useString(a[i+1:]) // ERROR "Proved IsSliceInBounds$"
 	}
 }
 
 func g3c(a string) {
-	for i := 0; i < len(a); i++ { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := 0; i < len(a); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		useString(a[:i+1]) // ERROR "Proved IsSliceInBounds$"
 	}
 }
 
 func h1(a []byte) {
 	c := a[:128]
-	for i := range c { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := range c { // ERROR "Induction variable: limits \[0,128\), increment 1$"
 		c[i] = byte(i) // ERROR "Proved IsInBounds$"
 	}
 }
 
 func h2(a []byte) {
-	for i := range a[:128] { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := range a[:128] { // ERROR "Induction variable: limits \[0,128\), increment 1$"
 		a[i] = byte(i)
 	}
 }
 
 func k0(a [100]int) [100]int {
-	for i := 10; i < 90; i++ { // ERROR "Induction variable with minimum 10 and increment 1$"
+	for i := 10; i < 90; i++ { // ERROR "Induction variable: limits \[10,90\), increment 1$"
 		a[i-11] = i
 		a[i-10] = i // ERROR "Proved IsInBounds$"
 		a[i-5] = i  // ERROR "Proved IsInBounds$"
@@ -153,7 +153,7 @@ func k0(a [100]int) [100]int {
 }
 
 func k1(a [100]int) [100]int {
-	for i := 10; i < 90; i++ { // ERROR "Induction variable with minimum 10 and increment 1$"
+	for i := 10; i < 90; i++ { // ERROR "Induction variable: limits \[10,90\), increment 1$"
 		useSlice(a[:i-11])
 		useSlice(a[:i-10]) // ERROR "Proved IsSliceInBounds$"
 		useSlice(a[:i-5])  // ERROR "Proved IsSliceInBounds$"
@@ -168,7 +168,7 @@ func k1(a [100]int) [100]int {
 }
 
 func k2(a [100]int) [100]int {
-	for i := 10; i < 90; i++ { // ERROR "Induction variable with minimum 10 and increment 1$"
+	for i := 10; i < 90; i++ { // ERROR "Induction variable: limits \[10,90\), increment 1$"
 		useSlice(a[i-11:])
 		useSlice(a[i-10:]) // ERROR "Proved IsSliceInBounds$"
 		useSlice(a[i-5:])  // ERROR "Proved IsSliceInBounds$"
@@ -182,7 +182,7 @@ func k2(a [100]int) [100]int {
 }
 
 func k3(a [100]int) [100]int {
-	for i := -10; i < 90; i++ { // ERROR "Induction variable with minimum -10 and increment 1$"
+	for i := -10; i < 90; i++ { // ERROR "Induction variable: limits \[-10,90\), increment 1$"
 		a[i+9] = i
 		a[i+10] = i // ERROR "Proved IsInBounds$"
 		a[i+11] = i
@@ -192,7 +192,7 @@ func k3(a [100]int) [100]int {
 
 func k4(a [100]int) [100]int {
 	min := (-1) << 63
-	for i := min; i < min+50; i++ { // ERROR "Induction variable with minimum -9223372036854775808 and increment 1$"
+	for i := min; i < min+50; i++ { // ERROR "Induction variable: limits \[-9223372036854775808,-9223372036854775758\), increment 1$"
 		a[i-min] = i // ERROR "Proved IsInBounds$"
 	}
 	return a
@@ -200,7 +200,7 @@ func k4(a [100]int) [100]int {
 
 func k5(a [100]int) [100]int {
 	max := (1 << 63) - 1
-	for i := max - 50; i < max; i++ { // ERROR "Induction variable with minimum 9223372036854775757 and increment 1$"
+	for i := max - 50; i < max; i++ { // ERROR "Induction variable: limits \[9223372036854775757,9223372036854775807\), increment 1"
 		a[i-max+50] = i   // ERROR "Proved IsInBounds$"
 		a[i-(max-70)] = i // ERROR "Proved IsInBounds$"
 	}
@@ -224,13 +224,13 @@ func nobce1() {
 }
 
 func nobce2(a string) {
-	for i := int64(0); i < int64(len(a)); i++ { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := int64(0); i < int64(len(a)); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		useString(a[i:]) // ERROR "Proved IsSliceInBounds$"
 	}
-	for i := int64(0); i < int64(len(a))-31337; i++ { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := int64(0); i < int64(len(a))-31337; i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		useString(a[i:]) // ERROR "Proved IsSliceInBounds$"
 	}
-	for i := int64(0); i < int64(len(a))+int64(-1<<63); i++ { // ERROR "Induction variable with minimum 0 and increment 1$"
+	for i := int64(0); i < int64(len(a))+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		// tests an overflow of StringLen-MinInt64
 		useString(a[i:])
 	}
@@ -239,7 +239,7 @@ func nobce2(a string) {
 func nobce3(a [100]int64) [100]int64 {
 	min := int64((-1) << 63)
 	max := int64((1 << 63) - 1)
-	for i := min; i < max; i++ { // ERROR "Induction variable with minimum -9223372036854775808 and increment 1$"
+	for i := min; i < max; i++ { // ERROR "Induction variable: limits \[-9223372036854775808,9223372036854775807\), increment 1$"
 		a[i] = i
 	}
 	return a

test/prove.go

@@ -62,7 +62,7 @@ func f1c(a []int, i int64) int {
 }
 
 func f2(a []int) int {
-	for i := range a { // ERROR "Induction variable with minimum 0 and increment 1"
+	for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1"
 		a[i+1] = i
 		a[i+1] = i // ERROR "Proved IsInBounds$"
 	}
@@ -464,7 +464,7 @@ func f16(s []int) []int {
 }
 
 func f17(b []int) {
-	for i := 0; i < len(b); i++ { // ERROR "Induction variable with minimum 0 and increment 1"
+	for i := 0; i < len(b); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1"
 		// This tests for i <= cap, which we can only prove
 		// using the derived relation between len and cap.
 		// This depends on finding the contradiction, since we