From b26ba6f760ad31149d7ef67c672d498595c61ac3 Mon Sep 17 00:00:00 2001
From: Nathan VanBenschoten <nvanbenschoten@gmail.com>
Date: Sun, 16 Jan 2022 04:39:18 -0500
Subject: [PATCH 1/2] apd: short-circuit in Context.goError

This commit adds a fast-path for the common case in `Context.goError`
that avoids the function call to `Condition.GoError`. `Context.goError`
is inlined in callers, so this avoids any function call in the common
case.

The commit also adds two addtional `gcassert:inline` directives.
---
 bigint.go  | 1 +
 context.go | 3 +++
 table.go   | 1 +
 3 files changed, 5 insertions(+)

diff --git a/bigint.go b/bigint.go
index 0d5737d..c50bb85 100644
--- a/bigint.go
+++ b/bigint.go
@@ -73,6 +73,7 @@ func NewBigInt(x int64) *BigInt {
 var negSentinel = new(big.Int)
 
 // isInline returns whether the BigInt stores its value in its _inline array.
+//gcassert:inline
 func (z *BigInt) isInline() bool {
 	return z._inner == nil || z._inner == negSentinel
 }
diff --git a/context.go b/context.go
index e84d330..260e092 100644
--- a/context.go
+++ b/context.go
@@ -81,6 +81,9 @@ func (c *Context) WithPrecision(p uint32) *Context {
 // goError converts flags into an error based on c.Traps.
 //gcassert:inline
 func (c *Context) goError(flags Condition) (Condition, error) {
+	if flags == 0 {
+		return flags, nil
+	}
 	return flags.GoError(c.Traps)
 }
 
diff --git a/table.go b/table.go
index 9abee51..d23dbd7 100644
--- a/table.go
+++ b/table.go
@@ -52,6 +52,7 @@ func init() {
 }
 
 // NumDigits returns the number of decimal digits of d.Coeff.
+//gcassert:inline
 func (d *Decimal) NumDigits() int64 {
 	return NumDigits(&d.Coeff)
 }

From c93277404fb42b7d41d565f01ebedfcf164d3876 Mon Sep 17 00:00:00 2001
From: Nathan VanBenschoten <nvanbenschoten@gmail.com>
Date: Sun, 16 Jan 2022 04:59:49 -0500
Subject: [PATCH 2/2] apd: inline Context.round

This commit reworks the call to `Context.round` to allow for mid-stack
function inlining. To do this, we remove the conditional call to one
of two functions, which is considered too complex to inline.
---
 context.go |  4 ++--
 round.go   | 15 ++++++++-------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/context.go b/context.go
index 260e092..0d3125d 100644
--- a/context.go
+++ b/context.go
@@ -1220,8 +1220,8 @@ func (c *Context) quantize(d, v *Decimal, exp int32) Condition {
 			// target eliminates this problem.
 
 			d.Exponent = -diff
-			// Avoid the c.Precision == 0 check.
-			res = nc.Rounding.Round(nc, d, d)
+			// Round even if nc.Precision == 0.
+			res = nc.Rounding.Round(nc, d, d, false /* disableIfPrecisionZero */)
 			// Adjust for 0.9 -> 1.0 rollover.
 			if d.Exponent > 0 {
 				d.Coeff.Mul(&d.Coeff, bigTen)
diff --git a/round.go b/round.go
index 92998c5..c9741a6 100644
--- a/round.go
+++ b/round.go
@@ -21,13 +21,9 @@ func (c *Context) Round(d, x *Decimal) (Condition, error) {
 	return c.goError(c.round(d, x))
 }
 
+//gcassert:inline
 func (c *Context) round(d, x *Decimal) Condition {
-	if c.Precision == 0 {
-		d.Set(x)
-		return d.setExponent(c, unknownNumDigits, 0, int64(d.Exponent))
-	}
-	res := c.Rounding.Round(c, d, x)
-	return res
+	return c.Rounding.Round(c, d, x, true /* disableIfPrecisionZero */)
 }
 
 // Rounder specifies the behavior of rounding.
@@ -63,12 +59,17 @@ func (r Rounder) ShouldAddOne(result *BigInt, neg bool, half int) bool {
 }
 
 // Round sets d to rounded x.
-func (r Rounder) Round(c *Context, d, x *Decimal) Condition {
+func (r Rounder) Round(c *Context, d, x *Decimal, disableIfPrecisionZero bool) Condition {
 	d.Set(x)
 	nd := x.NumDigits()
 	xs := x.Sign()
 	var res Condition
 
+	if disableIfPrecisionZero && c.Precision == 0 {
+		// Rounding has been disabled.
+		return d.setExponent(c, nd, res, int64(d.Exponent))
+	}
+
 	// adj is the adjusted exponent: exponent + clength - 1
 	if adj := int64(x.Exponent) + nd - 1; xs != 0 && adj < int64(c.MinExponent) {
 		// Subnormal is defined before rounding.